Abstract Laboratory tests were conducted to evaluate responses of an opiine fruit fly larval parasitoid, Diachasmimorpha kraussii (Fullaway), recently introduced to Hawaii for control of the solanum fruit fly, Bactrocera latifrons (Hendel), to four nontarget tephritid flies, including Trupanea dubautiae (Bryan), Ensina sonchi (L.), Eutreta xanthochaeta Aldrich, and Procecidochares utilis (Stone). T. dubautiae is a native Hawaiian tephritid, infesting flowerheads of the native composite shrub Dubautia raillardioides Hillebrand; E. sonchi is an adventive species, infesting flowerheads of the exotic weed, Sonchus oleraceus L. The other two tephritids, E. xanthochaeta and P. utilis, are deliberately introduced weed control agents, forming stem galls on Lantana camera L. and Ageretina adenphorum (Spreng), respectively. Gravid females of D. kraussii were confined in laboratory cages with host plant substrates (flowerheads or stem galls) infested with late instar larvae of the tephritid flies in both the presence and the absence of the normal rearing host, B. latifrons. Regardless of the presence or absence of B. latifrons, gravid D. kraussii showed some levels of positive visiting and probing responses to host plant substrates of all the test tephritids. Presence or absence of the normal hosts (B. latifrons) in the test cages had no significant effect on responses of gravid D. kraussii to the plant substrates. While a mean of 1.8 and 0.8 adult D. kraussii emerged per 10 exposed E. xanthochaeta galls (containing 10 fly larvae per trial) in both the absence and the presence of the parasitoid's normal hosts, no adult parasitoids were recovered from the other three tephritids. In all tests, D. kraussii normally emerged from B. latifrons, producing 8.6–16.3 wasps per trial (40 late instar B. latifrons larvae). Posttrial dissection of dead fly puparia and/or larvae revealed that for T. dubautiae, E. sonchi, and P. utilis, 2.3–5% of the dead fly pupae or larvae contained parasitoid cadavers (eggs and/or first instar capsules), whereas 15–26% of dead E. xanthochaeta pupae and larvae contained parasitoid cadavers. In contrast, 37.5–56.3% of dead B. latifrons pupae and larvae contained parasitoid cadavers, possibly because of superparasitism. Relevance of the findings to potential nontarget risks of using D. kraussii in fruit fly biological control programs is discussed.