The group continued to work hard and released several mixtape series which earned them a lot of attention in the rap industry. The most prominent of these being 50 Cent Is the Future, God's Plan, No Mercy, No Fear and Automatic Gunfire. G-Unit have also started a mixtape series with their DJ, DJ Whoo Kid, called G-Unit Radio.
Before the group had a chance to record its debut album, Tony Yayo was sentenced to prison for a gun-possession charge as well as bail-jumping. During Tony Yayo's prison sentence, the group signed Nashville rapper, Young Buck. They continued their activity, working on yet more mixtape recordings. In particular, their 'G-Unit Remix' to 50 Cent's "P.I.M.P." was successful.
During Tony Yayo's prison sentence, G-Unit recorded their debut album, Beg for Mercy. The album was quickly released on November 14, 2003 to combat bootlegging and had significant commercial success. Tony Yayo made only two appearances on the album, both on songs that were recorded before his arrest.
The Game was originally placed into G-Unit by Dr. Dre and Jimmy Iovine. However after a while tensions began to rise between G-Unit and the rapper. 50 Cent claimed that The Game was being disloyal to the group because he did not want to get involved with the feuds between G-Unit and other rappers, even going as far as to say that he wished to work with them. 50 Cent also felt that he did not receive enough recognition for the writing of tracks on The Game’s debut album. This resulted in what is arguably the biggest feud since the feud between Nas and Jay-Z. For more information see G-Unit vs. The Game feud.
On April 7, 2008, in an interview with Miss Jones on New York's Hot 97, 50 Cent stated that Young Buck was no longer a member of G-Unit but he was still signed to G-Unit Records. 50 Cent cited problems involving excessive spending and Young Buck's public claim to not being paid royalty cheques.
Their second album, T.O.S: Terminate on Sight, was released on July 1, 2008.
50 Cent also claimed that he was not getting his proper credit for the creation of the album. He also claimed that he wrote six of the songs, but The Game denied that. During that dispute, a member of The Game's entourage was shot after a confrontation at the Hot 97 studio in New York City. After the situation between them escalated, 50 Cent and The Game held a press conference to announce their reconciliation. Fans had mixed feelings as to whether the rappers created a publicity stunt to boost the sales of the two albums the pair had just released. Nevertheless, even after the situation had apparently deflated, G-Unit continued to feud with The Game, denouncing his street credibility in the media and claimed that without their support, he will not score a hit from his second album. The Game responded during a performance at Summer Jam and launched a boycott of G-Unit called "G-Unot". The phrase G-Unot is a pun on the group's name, and a pejorative term to refer to the group. It is short for "G (Gangster) You Not". 50 Cent has since registered the G-Unot trademark for himself which has in turn prevented The Game from using it anymore.
After the performance at Summer Jam, The Game responded with "300 Bars and Runnin'", an extended track aimed at G-Unit as well as members of Roc-A-Fella Records on the mixtape You Know What It Is Vol. 3. 50 Cent responded through his "Piggy Bank" music video, which features The Game as a Mr. Potato Head doll and also parodies other rivals. Since then both groups continued to attack each other. The Game released two more mixtapes, Ghost Unit and a mixtape/DVD called Stop Snitchin, Stop Lyin.
50 Cent's rebuttal was "Not Rich, Still Lyin'" where he mocks The Game. In addition, G-Unit started to respond on numerous mixtapes and new G-Unit member Spider Loc began insulting The Game in various songs. The Game responded with "240 Bars (Spider Joke)", a song mainly aimed at Spider Loc, but also addressing Tony Yayo and rap group M.O.P., and on the song "The Funeral 100 Bars".
In October 2006, The Game extended a peace treaty to 50 Cent, which was not immediately replied to. However, a couple days later, onPower 106, he stated that the treaty was only offered for one day. On The Game's album, Doctor's Advocate, he claims that the feud is over on a few of the songs. The feud seemed to have gained steam after Tony Yayo allegedly slapped the fourteen year old son of Czar Entertainment CEO, Jimmy Rosemond. The Game responded with "Body Bags" on his mixtape, You Know What It Is Vol. 4. G-Unit have released a song named "We On Some Shit" which is aimed at Czar Entertainment as well as Cam'ron and Fat Joe.
Since then, Black Child made two "disses" towards 50 Cent, "There's a Snitch in the Club", and "You the Wanksta". In both songs, Black Child talks about shooting 50 Cent, stabbing him, and other things, "I got a lot of living to do before I die, and I ain't got time to waste, shoot this nigga in his face".
The exchange of insultive tracks released from both parties culminated into Ja Rule releasing Blood in My Eye, which was an album that mostly insulted 50 Cent. Ja Rule eventually tried to squash the feud with 50 Cent by using minister Louis Farrakhan in a televised interview. However, the attempt at peace lost credibility as the interview was scheduled a day before Blood in My Eye was released. As a result, most fans, along with 50 Cent, dismissed the interview as a blatant publicity stunt. Because of the ongoing feud between the two, 50 Cent's labelmates Eminem, Dr. Dre and Obie Trice have also become involved and have also released tracks which insults Ja Rule.
Ja Rule later released R.U.L.E. with the successful single, "New York", featuring Jadakiss and Fat Joe in which Ja Rule took subliminal shots at 50 Cent. This single prompted 50 Cent to enter a feud with the two featured artists (see article on "Piggy Bank" for details).
Although it seemed that the feud was over, Ja Rule returned with a track entitled "21 Gunz". In response, Lloyd Banks and 50 Cent released the track "Return of Ja Fool" on Lloyd Banks' mixtape Mo Money in the Bank Pt. 4, Gang Green Season Starts Now.
50 Cent pointed out that Fat Joe painted a target on himself for partnering up with Ja Rule in a song where Ja Rule insulted 50 Cent. 50 Cent recorded the track "Piggy Bank" in which he attacked Fat Joe. Fat Joe responded with a track entitled "My 44" and although he said that he would not respond, he made three more tracks, "Massacre of Fifty", "Victim", and "Whip Your Head". 50 Cent and Tony Yayo took more shots at him on "I Run NY". Even though things died down, at the 2005 MTV Video Music Awards, Fat Joe mentioned that all of the police presence in the venue was "courtesy of G-Unit" which related to his lyrical accusations that 50 Cent was a "snitch". 50 Cent and Tony Yayo retaliated on set later in the show at the end of their performance by shouting obscenities towards Fat Joe and Terror Squad, which were censored by MTV. Tony Yayo claimed Fat Joe ran from them at the VMAs. Also, Pistol Pete (a non-rapping member of Terror Squad) appeared on The Game's "Stop Snitchin, Stop Lyin" DVD and disrespected Tony Yayo, Chris Lighty (owner of Violator Records whom had ties with 50 Cent), and James Cruz (50 Cent's manager) and claims he chased Tony Yayo near a jewelry store. Lloyd Banks, Spider Loc, and Young Buck have also been insulting Fat Joe. In 2007, the feud was continued in interviews and by affiliates from both parties. The feud has begun once again in 2008 with songs as videos being released from both parties. 50 Cent also released a mixtape entitled Elephant In The Sand, which is a mock title of Fat Joe's album Elephant In The Room. The front and back covers contain photos of Fat Joe on a beach.
A minor feud between G-Unit and DJ Khaled began when, on Rap City, DJ Khaled was asked to choose three classics out of a total of eight albums. He chose every album except Get Rich or Die Tryin'. This resulted in Young Buck releasing "Personal Unity", a track which insults DJ Khaled and Terror Squad. Young Buck also commented on the situation in an interview.