Macari's early career at Old Trafford was spent trying to lead an attack that struggled to achieve anything. Relegation to the 2nd division in 1974 was the low point but Macari blossomed as a midfielder in the following seasons under Tommy Docherty as United began to win back a large following with superb attacking football in which Macari enjoyed popularity alongside players such as Gordon Hill, Steve Coppell and the Greenhoff brothers.
After leaving United in 1984, he managed Swindon Town, West Ham, Stoke City (twice), Celtic, Birmingham City and Huddersfield Town.
His successes in management came with two promotions at Swindon Town (Fourth Division champions in 1986 and Third Division playoff winners in 1987) and a promotion with Stoke City (Division Two champions in 1993).
His sons Michael Macari and Paul Macari have played professionally with Stoke, when Macari was manager of the club. His youngest son Jonathan Macari committed suicide in 1999 after being released from his contract at Nottingham Forest.
Macari also owns the "Lou Macari Chip Shop" on Chester Road, near Old Trafford which is a popular takeaway on matchdays.