The company said the investment from Leeds Equity Partners would go into a fund to support public-private partnerships in higher education.
INTO, a British company founded by its owner Andrew Colin, has joint ventures with eight universities - including the University of East Anglia, University of Exeter and Newcastle University - providing foundation courses for international students.
Mr Colin said: "I am delighted to confirm today that we have secured this significant new funding to support the continued development of public-private partnerships.
"Today's higher education marketplace continues to face significant challenges driven by increasing budgetary constraints.
"Through public-private partnerships, there is a unique opportunity to meet the evolving and increasingly complex needs of universities and their students. In particular, our goal is to transform higher education capacity, increase access for well-qualified students, and drive global brand awareness by enhancing cultural diversity, all while delivering impressive outcomes for all stakeholders."
INTO's plan for a fund was launched in March last year, in a document featuring a foreword by former Labour education secretary Charles Clarke. Mr Clarke wrote that "expansion of educational opportunity across the world will only take place sufficiently quickly if private and public resources are brought together in partnership".
Mr Colin said: "Our unique approach has a proven track record of providing universities with a secure mechanism to unlock access to private capital while retaining full control over their academic standards and brand."
Leeds Equity Partners is a New York-based equity firm that "invests exclusively in the education, training and information and business services sectors" and has a "shared belief in the global expansion of university-led public-private partnerships", INTO's statement said.
Carter Harned, a managing director at Leeds Equity Partners, said: "In an era of soaring demand and declining public funding for higher education, INTO, working with its global network of world-class universities, is a strategic enabler. Its transformational model, supported by private sector investment, has already demonstrated its impact to major public universities on both sides of the Atlantic."