According to Official Guinness Records,
The most game wins by a coach in a National Basketball Association career is 1,333 by Don Nelson (USA) as of 8 April 2010. Nelson passed the previous mark of 1,332 set by Lenny Wilkens (USA) with a 116-107 victory by his Golden State Warriors over the Minnesota Timberwolves (both USA). Nelson's mark after his record-breaking win stood at 1,333 victories against 1,061 losses. His coaching career has spanned 31 seasons with five teams: the Milwaukee Bucks (540-344), New York Knicks (34-25), Dallas Mavericks (339-251) and Golden State Warriors (420-441).
For a complete list of 2010 records, please visit 2010 Guinness Records in United States.