The Manchester neighbours and rivals were joined by Swansea City, Watford and Crystal Palace in rejecting a proposal to move next summer's deadline forward to start of the season, per Sky Sports News.
The report also noted how United, City's and Swansea's votes were "in contradiction to their own managers Jose Mourinho, Pep Guardiola and Paul Clement."
While United, City and others weren't in favour, 14 other Premier League clubs voted for ending next summer's transfer window on Thursday, August 9 2018, according to Lyall Thomas of Sky Sports.
With 14 clubs approving, it means a two-thirds majority was secured to change the parameters of the summer window, starting in 2018. It means all clubs will have to have their business done before the start of the season.
It's a decision sure to win applause from many managers who usually find the start to a season disrupted by continued speculation about the future of their own players. There is also the added distraction of fans calling for more signings up to and during deadline day, traditionally at the end of August, even while league matches are being played.
Guardiola will be among those in favour of the new rule, even if his club isn't. He called for the deadline to be moved forward back in July, per Jim White of TalkSport.
Arsenal manager Arsene Wenger has also already backed the idea, per Charles Watts of Football.London:
"We should close all that stuff before the Championship starts. It's not the way to work, it's uncomfortable and every single manager in the league would agree it's time to kick that out before the season starts.
"We can't have players who are half out and half in."
With the summer deadline now moved, focus may turn to altering the pattern of the January transfer window.
Wenger called for an end to the annual winter spending period, per beIN Sports (h/t The Independent): "The players who do not play or the players who are tapped up in October they already start again to think: 'Where do I go in January?'. That's not a way to be on board with a football club..."
Given how readily many clubs supported changes to the summer transfer setup, January's window could be in line for a major shakeup if it comes to a vote.