The liberal judge, who at 85 is the oldest US Supreme Court justice, was treated in hospital after falling in her office, a court spokesperson said.
Justice Ginsburg went home after the accident but later felt uncomfortable and went to George Washington University hospital the following morning, Kathy Arberg said.
Tests showed she had fractured three ribs on her left side. She was then admitted for observation and treatment, Ms Arberg added.
Her nephew, a filmmaker who has just completed a film based on his aunt’s life, said she was already cracking jokes.
At the premier of his film On the Basis of Sex, about a gender discrimination case Justice Ginsburg tried as a lawyer in 1972, Daniel Stiepleman said: “The last I heard she was up and working, of course – because what else would she be doing – and cracking jokes.”
“I can’t promise they were good jokes but they were jokes,” added Mr Stiepleman, who wrote the script for the film with input from Justice Ginsburg herself.
Justice Ginsburg was appointed to the Supreme Court in 1993 by Bill Clinton. Prior to the appointment she spent a considerable part of her legal career as an advocate for gender equality and women’s rights.
She is one of four liberal judges appointed to the court. The 5-4 conservative majority was restored earlier this year with Donald Trump’s appointment of Brett Kavanaugh.
If Justice Ginsburg were unable to keep serving, Mr Trump could replace her with another conservative, tipping the balance even further to the right.
A potentially dominant 6-3 conservative majority would have major consequences for issues including abortion, the death penalty, voting rights, gay rights and religious liberty.
As the oldest Supreme Court judge, Justice Ginsburg is watched closely for any signs of deteriorating health.
She has bounced back from previous medical issues and has fallen twice before at her home, in 2012 and 2013, leading to rib injuries.
She was treated in 1999 for colon cancer and again in 2009 for pancreatic cancer, but did not miss any argument sessions either time.
In 2014, doctors placed a stent in her right coronary artery to improve blood flow after she reported discomfort following routine exercise. She was released from hospital the next day.
The court next convenes to hear evidence on 29 November.
She is a hero among many Democrat voters, with whom she has the nickname “the Notorious RBG”.
A documentary film about her, RBG, was released earlier this year, and her nephew’s Hollywood biopic will be released at Christmas.
Reuters contributed to this report