32 times.
This includes 17 wins and 15 losses in the post-season.
They have appeared in the playoffs 20 different seasons (though some seasons saw them win multiple post-season games).
Through the 2011 season the Cowboys have made the playoffs in 30 seasons. 1966, 1967, 1968, 1969, 1970, 1971, 1972, 1973, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1985, 1991, 1992, 1993,...