There were 2,717 households out of which 33.8% had children under the age of 18 living with them, 55.2% were married couples living together, 9.9% had a female householder with no husband present, and 30.8% were non-families. 27.2% of all households were made up of individuals and 13.8% had someone living alone who was 65 years of age or older. The average household size was 2.52 and the average family size was 3.08.
In the city the population was spread out with 26.8% under the age of 18, 9.6% from 18 to 24, 27.6% from 25 to 44, 19.6% from 45 to 64, and 16.4% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 95.9 males. For every 100 females age 18 and over, there were 88.6 males.
The median income for a household in the city was $35,817, and the median income for a family was $44,385. Males had a median income of $32,917 versus $21,124 for females. The per capita income for the city was $16,380. About 5.6% of families and 6.8% of the population were below the poverty line, including 7.5% of those under age 18 and 6.6% of those age 65 or over.
Delphos City Schools include Jefferson High School. Jefferson High School, the Wildcats', sports participate in the Northwest Conference, an athletic body sanctioned by the Ohio High School Athletic Association (OHSAA), which includes the Ada Bulldogs, Allen East Mustangs, Bluffton Pirates, Columbus Grove Bulldogs, Convoy Crestview Knights, Delphos Jefferson Wildcats, Lima Central Catholic T-Birds, Lincolnview Lancers, Paulding Panthers, and Spencerville Bearcats.
Delphos St. John's High School, the Blue Jays, has 14 Ohio state championships, 4 of which are football championships (tied for fourth most in Ohio) among boys and girls basketball, track, football, and golf. On March 10, 2007, the Delphos St. John's girls basketball won a game against Columbus Grove to become Regional Champions for the ninth time. Additionally, its football team holds the Ohio state record for most consecutive wins, at 57, from 1 November 1996 to 17 November 2000. St. John's High School is part of the Midwest Athletic Conference.