Very little is known about this species, with only a handful of observations and camera trap records. Available information suggets that, like its close relative the fishing cat, the flat-headed cat is strongly associated with wetlands and preys primarily on fish. Stomach contents of two dead animals contained mostly fish, and also shrimp shells. They may also take birds and small rodents, and have been reported to prey on domestic poultry (Nowell and Jackson 1996).

Most records for the Flat-headed Cat are from swampy areas, lakes and streams, and riverine forest (Nowell and Jackson 1996, Yasuda et al. 2007). They also occur in peat-swamp forest (Bezuijen 2000), and have been observed in secondary forest (Bezuijen 2000, Bezuijen 2003, Meijaard et al. 2005, Mohamed et al. 2009). All published observations of live animals have taken place at night or early morning, near water (Nowell and Jackson 1996, Bezuijen 2000, Bezuijen 2003, Meijaard et al. 2005, Yasuda et al. 2007). Over 80% of the records gathered by Wilting et al. (2010) were from elevations below 100 m asl, and over 70 % were recorded within a distance of 3 km to larger water sources.

The Flat-headed Cat takes its name from its unusually long, sloping snout and flattened skull roof, with small ears set well down the sides of its head. It has large, close-set eyes, and relatively longer and sharper teeth than its close relatives. Its claws do not fully retract into their shortened sheaths, and its toes are more completely webbed than the fishing cat's, with long narrow foot pads. Muul and Lim (1970), commenting on the cat's feet and other features, termed it the ecological counterpart of a semi-aquatic mustelid.