Chris Wood put Millwall two up with a well-taken brace but Brighton sub Kazenga LuaLua pulled one back before David Lopez's late penalty denied the visitors the chance to move up to fifth..
Jackett said: "Brighton are a very, very good side and probably the best team we have played.
"But I'm pleased with the performance and result. We created a number of chances in the first half and then we came under pressure. I was pleased that we took something from the game."
Jackett was forced to make a late change before kick-off by bringing in Jack Smith into the midfield in place of injury victim Andy Keogh.
"Unfortunately, Andy has a broken toe and we couldn't inject it," he added.
"We had to change the team because Andy didn't feel good enough to play. The squad has to adapt and Jack Smith came in and delivered an excellent performance."