The deal, for an undisclosed sum, means Normanton-based Sandford has added creative and content services to its work in e-commerce, software application development and online security.
Leap Frog designs websites for public and private sector clients throughout the UK. Set up eight years ago, its client portfolio covers the industrial engineering, leisure, finance, retail, tourism, housing and technology sectors.
Richard Atkinson, managing director of Sandford Technology, said: "We're delighted by our acquisition of Leap Frog. It's good news for our businesses, as it will enhance their capabilities, and our clients will benefit from having a complete range of IT services under the same roof."
Anthony Jones, business development manager at Leap Frog, added: "The merger is a great leap forward for the future of the business."
Leap Frog has relocated from Halifax to Normanton but will continue to trade under its own brand.
With the acquisition of Leap Frog, Sandford expects to increase its turnover to £1m in 2006/7.