Double-amputee runner Pistorius, who goes on trial on a murder charge next month, was arrested and accused of causing an injury to a guest at a party at his house five years ago after allegedly slamming a door and then punching it.
Pistorius family spokeswoman Anneliese Burgess said the settlement agreement was finalised late last year with Cassidy Taylor-Memmory, who accused Pistorius of assault in the September 2009 incident. Ms Taylor-Memmory was reportedly injured in the leg when the door broke.
"The reasoning for the settlement being that Oscar was advised by his lawyers that he could not run a civil and criminal matter (side) by side," Ms Burgess said in a statement to the Associated Press. The matter had "no bearing" on Pistorius's murder trial, Ms Burgess said, and was settled "solely for the purposes of expediency".
Ms Burgess did not give any details of the settlement.
Pistorius will go on trial from March 3 on a charge of premeditated murder for the killing of his girlfriend Reeva Steenkamp at his home last February 14, and also faces other firearm-related charges at the trial at a high court in the South African capital, Pretoria. He denies murder and claims he shot Ms Steenkamp by mistake after believing she was a dangerous night-time intruder in his bathroom.
Pistorius's lawyers are also in negotiations with the family of Ms Steenkamp over another out-of-court settlement ahead of his murder trial.
Regarding the 2009 case, Pistorius had launched a counter-claim against Ms Taylor-Memmory, accusing her of making up the assault. He said he was arrested without reason.
The settlement with Ms Taylor-Memmory was first reported in South Africa by Eyewitness News, which quoted her as saying Pistorius agreed to pay her legal fees and also drop his counter-claim against her.
"I agreed to it because I was so tired of it weighing me down," Ms Taylor-Memmory told Eyewitness News, claiming she was harassed by the media and the public and received hate mail. "It became so difficult at a stage that I needed a bodyguard when I went out in public due to all the hate rants," she said, according to Eyewitness News.
The 2009 arrest is when Pistorius is believed to have first come across former detective Hilton Botha, one of the first police investigators to examine the scene after Pistorius shot Ms Steenkamp last Valentine's Day - a year ago on Friday.
After Ms Steenkamp's shooting death, police said there had been previous incidents "of a domestic nature" at Pistorius's upscale Pretoria house without elaborating on them.