Nicola Tustain won the bronze in the grade II individual dressage to take Britain's equestrian medal tally to four on Wednesday. She scored 68.727% on Prinz Heinrich but was overtaken by Irene Slaettengren of Sweden and Holland's Joop Stokkel.
The 26-year-old won bronze in the same event in Sydney four years ago.
"I was very pleased with my performance," she said. "I felt I rode the best I could and my horse went as well as he could."
Tustain, who earlier this year was named the Laureus World Sportsperson of the Year with a Disability, notched up two gold and one bronze in Sydney and is expecting more success at this Games
"The programme for the freestyle on Friday is more challenging which will help me as long as I can keep the quality of walk and trot," she added.
Meanwhile fellow Briton Jo Pitt finished joint eighth overall.
"This is my first Paralympic participation and I'm more excited than nervous," she said.
"I'm pleased with my performance and I think the Paralympic Games is a great challenge for us competitors."
Tustain's result is also important for Britain's bid to continue its domination of the team dressage competition.
She is one of four GB riders whose individual scores count towards the team event, along with Lee Pearson and Deborah Criddle - both gold medalists on Tuesday, and Anne Dunham.