Uganda-born Sekajja has joined in time to make his debut in Wednesday night's home clash against Leyton Orient in League One.
Manager Karl Robinson has been open about his desire to bring in a forward with natural pace in recent weeks and he appears to have got his man in the shape of the 20-year-old.
The Dons boss told Dons' official website: "We have been looking at Ibra for some time now, he is a player who has come on leaps and bounds at Crystal Palace in the last few months.
"I spoke to Dougie Freedman (former Palace boss) on a number of occasions about him because he's exactly what we need in the team at the moment - he is young, fearless and fast.
"We watched Ibra play against Middlesbrough's Development team on Monday night and I am delighted Ian Holloway (new Palace boss) has allowed one of his starlets to join us for the next two months."