The 31-year old Australian striker has headed back to Fir Park, this time as a free agent, after leaving Millwall earlier this season.
McDonald spent three years with the Steelmen between 2004 and 2007, scoring 42 goals, before moving to Glasgow giants Celtic where he enjoyed plenty of success.
Of the move, McDonald said he could have gone elsewhere overseas but opted to return to a club that he holds very dear to his heart.
"That was the main reason I chose to come back here. I had a lot of special times here and this is pretty much where it all began for me and kicked on my career," said the former Middlesbrough man.
"I'm looking for that again, and I hope we can do something successful until the end of the season. It's been a tough season up until now for Motherwell, so hopefully we can change that around.
"Obviously I know a few people here and they became aware of my situation. I was a free agent and I had a couple of offers from abroad, but for me at this moment in time that's not really the path I want to take.
"I still see my career in the British game, and once they came in with an offer straight away I said yes. Like I said this place is like family to me and Scotland's been so good to me, so it was a no-brainer to come back here."
"I've been around for quite so time now. It's quite a youthful squad, we have a couple of players that I have played with before, so it will just be like stepping into old times for me."
Motherwell FC (@MotherwellFC) February 26, 2015
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