Low test-taking effort as a validity threat is common when examinees perceive an assessment context to have minimal personal value. Prior research has shown that in such contexts, subgroups may differ in their effort, which raises two concerns when making subgroup mean comparisons. First, it is unclear how differential effort could influence evaluations of scale property equivalence. Second, if attaining full scalar invariance, the degree to which differential effort can bias subgroup mean comparisons is unknown. To address these issues, a simulation study was conducted to examine the influence of differential noneffortful responding (NER) on evaluations of measurement invariance and latent mean comparisons. Results showed that as differential rates of NER grew, increased Type I errors of measurement invariance were observed only at the metric invariance level, while no negative effects were apparent for configural or scalar invariance. When full scalar invariance was correctly attained, differential NER led to bias of mean score comparisons as large as 0.18 standard deviations with a differential NER rate of 7%. These findings suggest that test users should evaluate and document potential differential NER prior to both conducting measurement quality analyses and reporting disaggregated subgroup mean performance.