Soup, which is based in London and Norwich, has 35 staff. Its clients include Sky, Innocent, Jordans Cereals, Virgin Money, Moonpig and Aviva.
Skive and Soup will continue to operate as separate entities, but will share certain resources when required.
Separately, ad industry veteran Alan Page has been appointed as Skive's new chairman.
Page was the creative director of Yellowhammer, a founder of ad agency Harari Page, and more recently created digital marketing group, New Media Industries.
His appointment reflects the company's determination to strengthen all parts of its operation in the wake of new business growth.
Late last year, Skive won Nestle's online campaign for KitKat and earlier this year created the 'Start Thinking Soldier' campaign for The British Army's digital recruitment programme.
Page said "We see [the Soup acquisition] as the first step of our strategic plan to develop a broader independent digital marketing offering.
"As Skive increases its direct relationships with clients, the exceptional skills of Soup in strategic planning and creative will provide the group with a chance to continue developing its own skills in these areas. Also, the deal places the combined group in the top 40 agencies in the UK."
Nick Thompson, managing director of Soup, said, "This is a great opportunity to take the business forward with like-minded people.
"Skive is ambitious, has strong credentials, a reputation for delivering high quality work and is passionate about digital. We are all excited about moving forward together."