Many workers today are employed under a variety of nonstandard work arrangements, such as contract work and agency temporary work. While prior research has shown that the use of nonstandard workers can be detrimental to standard workers' attitudes and behaviors, producing conflict between nonstandard and standard employees, that research has not shown how or why. We propose a model in which threat to status of, and accommodation by, standard workers cause negative reactions to nonstandard workers, contingent upon the competence of nonstandard workers. The model helps explain how subtle differences among seemingly similar nonstandard work arrangements can produce dramatically different challenges to work group effectiveness. Implications for the effective blending of work groups are discussed.