The victory in just over two hours was the third in mixed for the 40-year-old Nestor, who teamed with his 20-year-old partner starting at the French Open a month ago.
The new pair lost the final at Roland Garros, but quietly made their way through the Wimbledon draw, saving two match points in the final.
"I'm fortunate to play with someone that can more than do her share," said Nestor. "She's a great player. She's going to be one of the top singles players eventually. Right now I'm catching her while she's maybe not winning four or five matches in singles. She's winning two or three, so hopefully that will change for her.
"Right now, you know, she's focusing on doubles and mixed. I think that will change one day. I caught her at the right time."
Nestor also won the mixed crown at the 2007 Australian Open with Russian Elena Likhovtseva and in 2011 in Melbourne with Katarina Srebotnik. The Wimbledon honour was the 81st career title for the Canadian, who also won the men's doubles title twice.
Nestor and his teammate, seeded eighth, dropped the 41-minute opening set on a late break, but quickly began a comeback early in the second with a break for 2-1.
Mladenovic, watched by good friend and women's Wimbledon winner Marion Bartoli, played superb defence for the team as they broke Suarez for 4-1 and levelled the sets at one apiece as Nestor fired over an easy putaway volley.
The third set was tight as the contest stayed with serve. The Canadian-French team saved a pair of match points in the 12th game with a winner and then profited on a Suarez error to reach 6-all in the play-it-out format.
Suarez dropped serve again as the top seeds trailed 6-7. A game later, Nestor wrapped up the win after a Mladenovic wrist volley clipped the net low on a first match point. The Canadian then produced a stinging backhand winner to spell the end.