In two spells over seven years, the Portuguese won the Premier League and League Cup on three occasions and an FA Cup.
But seven months after winning the league in 2015, Mourinho was sacked following a dismal start to last season.
A Chelsea statement claimed there was a “palpable discord between manager and players” which forced the club to dismiss their most successful boss.
And eight months later, judging by the clip, there still appears to be some ill-feeling.
While in China with his United squad on their pre-season tour, Mourinho was asked by a supporter to sign a Blues shirt.
But he flatly refused, shaking his head at the individual as he approached the jersey.
Mourinho is in Shanghai for the first of two United matches in the Far East.
The first sees his side face Borussia Dortmund tomorrow (1pm) before meeting neighbours Manchester City at the Beijing National Stadium on Monday.