Some of the funding is going towards buying the shares of founder Michael Bruno, according to the publication.
The investment will also help New York-based 1stdibs, a portal hosting more than 2000 dealers in exchange for subscription and listing fees, continue expanding overseas and move into e-commerce.
A 1stdibs spokesperson told ATG that Fortune's estimate of the Insight Venture Partners funding was incorrect but confirmed "a recent round of financing" that would be used to fund growth and generate buyers for dealers on the site.
Now in 17 geographical markets, 1stdibs acquired UK dealer portal Online Galleries in 2012 and, in 2014, received $15m in funding from Chinese e-commerce giant Alibaba.
1stdibs was founded in 2001 by Bruno after he visited Paris antiques market Marché aux Puces and saw an opportunity for French dealers to reach US buyers via an online marketplace.
Fortune reports that IVP's investment values 1stdibs at $300m (£194.4m) and that revenue for 2014 was $30m.