The 53-year-old left with the club bottom of League Two and in danger of losing their Football League status.
Adams' number two Alan Rogers and academy boss Shaun Garnett have been put in charge for the final two games of the season.
Rovers are one point behind Cheltenham and two adrift of Hartlepool United.
Two of those three teams will be relegated, with Tranmere having the superior goal difference should that be the deciding factor.
They face play-off contenders in their final two matches - travelling to Plymouth next Saturday before a home game against Bury a week later.
"We thank Micky for his work at Tranmere Rovers, having taken over at a difficult time, and wish him all the best for the future," said a club statement.
Adams took charge at Prenton Park last October, having left Port Vale the previous month.
He has achieved four promotions in a managerial career which began at Fulham in 1996, but won only 10 of his 38 games in charge of Tranmere, with 17 ending in defeat.
Their last victory came at Cambridge on 17 March, and the 3-0 loss to Oxford was their fourth defeat in a row.
Adams did not attend the post-match media conference, at which Rogers said: "It's a great club with great supporters, but what they're seeing is not good enough."
Tranmere were relegated from League One on the final day of last season, when they were beaten 2-1 at home by Bradford City. Ironically, Hartlepool are managed by Ronnie Morre who was sacked by Tranmere only 18 months ago following his admission of placing bets in a betting shop.