Felicia Sonmez posted a link to a 2016 article about the allegations, and received death threats online. She was later suspended over the tweets - prompting hundreds of her colleagues to condemn the paper. Managing editor Tracy Grant called the posts "ill-timed", but said they did not break the paper's policies.
"We consistently urge restraint, which is particularly important when there are tragic deaths," her statement read. "We regret having spoken publicly about a personnel matter."
More than 300 Washington Post employees signed a letter in support of Ms Sonmez on Tuesday, including Pulitzer Prize winners David Fahrenthold and Beth Reinhard, and White House Bureau Chief Philip Rucker.
The Washington Post Guild welcomed the decision to reinstate the reporter, although said it was "disappointed" that the paper did not apologise to Sonmez and said the company should prioritise staff safety in the future.
And Sonmez herself called on chief editor Marty Baron to explain why the paper handled the issue as it did, and stressed that she had tweeted about "a matter of public record".
Baron wrote an email to Sonmez after the tweets saying she had shown "a real lack of judgement", and saying she was "hurting this institution by doing this".
Sonmez tweeted a 2016 Daily Beast story about the rape allegations against Kobe Bryant just hours after the basketball legend died in a helicopter crash that killed nine people - including his 13-year-old daughter Gianna.
Over the course of a 20-year career Bryant won five NBA championships and two Olympic Gold medals, and is considered one of the greatest players in the history of the sport.
In 2003, Bryant was accused of sexual assault by a 19-year-old woman. The case was dropped after she refused to testify in court. She had received death threats after a clerical error saw her name published online.
Bryant repeatedly denied the allegations but later apologised and settled a civil case out of court.
In a statement delivered by his lawyer on the day the criminal case was dropped, Bryant apologised to the woman, adding that he understood "how she feels that she did not consent to this encounter".