Nqual was set up in 2005 to give clients the ability to conduct qualitative surveys online, as a more practical and cost effective method of data capture than face to face interviews.
Nqual employs researchers and IT professionals to conduct the surveys, which claim to give genuine insight into the consumer.
The investment bolsters Cello's online research offering, which previously amounted to its existing data capture businesses FML, Kudos and Digital People.
Mark Scott, chief executive at Cello, said: "Cello has transformed over the past two years into a large research and consulting business, with real strength in qualitative research across a number of client sectors.
"Online research is fundamental to our growth, and the relationship with Nqual allows us to further enhance the online solutions we can offer our clients."
Cello also owns Edinburgh-based groups Navigator, The Leith Agency, Stripe, and Farm Communications, and recently announced a rise in turnover for 2006, which is up by 43% to £74.7m.