Seedorf was tasked with rescuing a disappointing season after being named as Massimiliano Allegri's replacement in January, but was sacked at the end of the campaign after finishing eighth in Serie A.
And Tassotti says their working relationship was so bad that he considered leaving the Serie A club.
"It wasn't an easy relationship," he told Gazzetta dello Sport. "But that is all in the past so it's useless talking about it.
"I haven't spoken to him since it happened. I tried to work with him in the best way possible.
"But you have to feel like it's a collaboration, and feel easy working together – it didn't feel like that.
"I was very close to leaving Milan, but then I was told that there would be a new man coming in and I was wanted as part of the coaching staff.
The 54-year-old, who won three European Cups during his 17-year spell with the club as a player, says he is now happy to remain in the role after speaking to new coach Filippo Inzaghi.
"I spoke with Pippo and with the club, and I have decided to stay."