Twitter did not disclose financial terms of the deal, which technology news website Re/code said was valued at more than $30 million (roughly Rs. 187 crores).
"As more users and creators use different products as a way to share what's happening in their world, brands are also looking to partner with those individuals in hopes of generating moments that resonate with the people they are trying to reach," said Twitter director of product management Baljeet Singh.
Niche was launched in late 2013 and soon began working with Twitter, which owns the Vine app for sharing short, looping videos online.
The world of social media has grown to include people who have become celebrities by posting clever, funny, or fascinating looping video snippets using Vine or Facebook-owned Instagram.
Niche boasted it has more than 6,000 "social media creators in its growing stable of talent.
"All across the world, comedic personalities, aesthetic photographers, visual artists, foodies and fashionistas have leveraged new mobile platforms to build vast and direct fan bases," Niche said in an online post.
Niche, which has offices in San Francisco and New York City, describes itself as more than just a talent agency for social media stars.
The company said it provides analytics to back online popularity, whether fans visit from desktop and mobile devices, and fosters partnerships between video makers and brands seeking ways to connect with online audiences.