Following the acquisitions, Endemol's UK subsidiary is expected to overtake All3Media to become the largest independent producer in Britain, with an annual turnover of around £250m.
Tiger Aspect produces a range of drama, comedy and factual shows, including Harry And Paul, Benidorm and Ross Kemp On Gangs.
Darlow Smithson specialises in high production feature documentaries, such as The Falling Man, Miracle On the Hudson and Touching the Void. The deal also includes Darlow subsidiary Tigress, which specialises in wildlife and science shows.
"We're extremely excited about working with three of the most successful and creative production companies in the UK," said Endemol UK chief executive Tim Hincks, who all three companies will now report to.
"They represent a collection of some of the best creatives in the business and are behind a dazzlingly wide range of genres. We want to back them and give them the freedom to further grow, both in the UK and around the world."
Tiger Aspect managing director Andrew Zein said: "Endemol is the real deal - a fully functioning global creative business. They understand and appreciate what we do and how we do it. For us this is the dream deal we thought would never happen. We've found the ideal home."
Darlow Smithson and Tigress executive chairman John Smithson added: "This is an exciting opportunity for both Darlow Smithson and Tigress. We can enjoy creative freedom while having all the benefits of being part of a global media player."
US marketing firm IMG bought Tiger Aspect and Darlow Smithson in 2006 as part of a strategy to expand beyond its traditional sports broadcasting arena. However, it opted to put the divisions up for sale earlier in the year.
"These companies have never been synergistic with IMG's core business," said IMG executive vice president and chief financial officer Chris Davis.
"We believe they are an excellent fit with Endemol's global network of companies and we wish them, their managements and employees great success in the future. IMG will continue to focus its resources on its exceptional global core capabilities including further expansion into large new high growth markets."