One-time boom horse Prince Harada has returned from more than a year away from racing to score a first-up win at Caulfield.

Prince Harada stepped out for his first start as a gelding in Saturday's theshark.com.au Handicap (1100m) and in his first race since last year's Australian Guineas the four-year-old arrived in time to beat Boomwaa by a short half-head.

Prince Harada won his first two starts as a late-season two-year-old when trained by Tony Vasil and was touted as one of the most promising three-year-old's heading into last season.

He was a luckless second in the McNeil Stakes before finishing fifth in the Golden Rose and sixth in the Caulfield Guineas.

He joined trainer Danny O'Brien's team after his autumn campaign last year when Vasil took a break from training.

Saturday's race was Prince Harada's first start for O'Brien after the gelding missed the spring because of minor knee soreness.

"He just had a couple of niggles so we gave him time and I think it was the best thing for the horse," O'Brien's stable representative Matt Harrington said.

"He looks sensational and I'm very happy for the owners who have been patient for us and it's good to repay them today.

"He's been trialling really well but you want to see him do it on raceday, so that was good to see."

Prince Harada settled just better than midfield with a three-wide trail and jockey James Winks had the $2.80 favourite in the clear from the top of the straight.

Prince Harada ran his last 600m in 33.35sec to get home in front of leader Boomwaa ($4.60) with Agent ($31) another half length away third.

Winks said Prince Harada did a lot wrong before the race but was still good enough to win and hopes he can go to greater heights now.

"He's blown the cobwebs out. He's only going to improve. He's a lovely horse," Winks said.