The 53-year-old, who managed the Jambos between July 2008 and January 2010, takes over from Ray McKinnon at Tannadice Park until the summer of 2019.
McKinnon was sacked in October following back-to-back Scottish Championship defeats, leaving the club fourth in the division at the time.
United have since beaten Dumbarton and St Mirren to move into second place, however, and chairman Stephen Thompson hopes that Laszlo - who finished third with Hearts in his one full Scottish Premiership season - can take the club back up.
"After meeting Csaba, seeing his enthusiasm for the job and his understanding of what is required by Dundee United, he emerged as the outstanding candidate," he told Dundee United's official website.
"Csaba's CV is very impressive and his enthusiasm very infectious but after we met, the Board spoke to many people who had worked with him in football and I believe we have secured a fantastic coach, man-manager and a highly experienced tactician. I am delighted to welcome him as the new Dundee United manager."
Laszlo's last stint in management was with Slovakian side Dunajska Streda, having also taken in spells with Uganda and Lithuania at international level in recent times.