Clijsters, who had been sidelined with shoulder, wrist and ankle injuries since early last month, said Wednesday's first training session was completed without pain.
The Belgian ruled out playing any tournament ahead of the French Open, which opens on May 22.
"I held a tennis racket in my hands for the first time in about five weeks. It felt good," she said on her website Thursday.
During a busy early spring schedule, Clijsters overexerted her right shoulder and wrist. She also injured her right ankle while wearing high heels at her cousin's wedding.
Wednesday's first outing on court "went well, without pain or trouble. But I didn't put too much pressure on my ankle," she said.
Clijsters' immediate future and participation in the French Open remain up in the air.
"It depends on a great many factors: What is the reaction to the first days of training? What if we increase the training intensity?" she said.
Clijsters has already pulled out of next week's Italian Open but, despite her extended time away from the tour, remains No. 2 in the world rankings behind Caroline Wozniacki of Denmark.
Clijsters is a two-time runner-up at the French Open and slow clay is generally considered her weakest surface.
Coming in cold into the biggest clay tournament in the world would count heavily against her. She was already forced to miss the tournament last year.
The grass of Wimbledon suits her game better and she has already signed up to compete in a warmup tournament in Rosmalen, Netherlands.