We studied the summer (June–August) diet of the masked palm civet (Paguma larvata) in a suburban area of Ibaraki Prefecture, using the stomach contents from road-killed carcasses. Specifically, our aim was to examine (i) monthly changes and (ii) if food habits differed between sexes, based on frequency of occurrence (FO) of the main food classes consumed. From 2009 to 2014, 61 civet carcasses were collected along the three major national highways in Ibaraki Prefecture. Civets consumed a wide range of foods such as insects, fruits, mammals, and earthworms. The FO of mammals and fruit taxa (cherries, strawberries, and persimmons) differed substantially among months, which likely reflected the peak availability of each food category/item. Females consumed amphibians, insects, and persimmons significantly more frequently than did males, likely relating to the higher food security demands of females while raising offspring. Overall, masked palm civets in Ibaraki Prefecture proved to be opportunistic and generalist feeders, eating primarily fruits and insects with a high frequency of occurrence in summer.