Milligan and one of his daughters were killed on Sunday in a boating accident in Cornwall. He leaves behind a wife, two daughters and a son.
Darroch said: "Everyone at Sky is devastated by the tragic loss of Nick Milligan. As I reflect on my memories of Nick, it is his integrity, professionalism and charm that shine though.
"Nick made a very significant contribution to our business and the wider TV industry. He was a hugely popular figure both within Sky and across the industry."
Darroch also credited Milligan, one of the most prominent figures in British commercial television, as a great mentor and role model, particularly to young people entering the business, and with transforming Sky Media.
"He created a brilliant team in London, Manchester and Dublin and was rightly proud of this achievement," Darroch said.
"Along the way, Nick touched the lives of many people here at Sky and beyond. Nick was a key part of the Sky story and his legacy will endure."
Milligan started his career at TVS in 1983 and spent the next 30 years working for various commercial TV companies. He was a launch member of UK Gold in the early 90s.
Before moving to Sky Media in 2004, Milligan worked at Channel 5, having joined the broadcaster as one of its founding directors in 1996 – the year before it launched. During his time at Channel 5, he spent a period as the acting chief executive when Dawn Airey became the managing director of Sky Networks.
However, when Jane Lighting took the chief executive job, he followed Airey to Sky in 2004.