Parents of children with neurodevelopmental conditions (NDC) are at risk of experiencing elevated levels of parental stress. Access to robust instruments to assess parental stress is important in both clinical and research contexts. Objective: We aimed to evaluate the psychometric properties of a Swedish version of the Parental Stress Scale (PSS), completed by parents of 3- to 17-year-old children, with and without NDCs. Main analyses were conducted on data from three independent samples: a community sample (n=1018), a treatment-seeking sample of parents of children with various disabilities (n=653), and a sample of parents of children with Attention-Deficit/Hyperactivity Disorder (ADHD) who themselves reported varying ADHD symptom severities (n=562). Additional analyses were enabled by the use of data from a complementary test-retest sample (n=337). The internal consistency of the PSS was good (Cronbach's alpha, α=.87) and its test-retest reliability moderate (ICC=.66). The scale correlated in the expected direction with related constructs (r=.50-.56 in the community sample). An exploratory factor analysis found its internal structure to reflect two aspects of parental stress: Lack of Parental Rewards and Role Satisfaction (factor 1, α=.90) and Parental Stressors and Distress (factor 2, α=.85). The treatment-seeking parents of children with disabilities reported higher parental stress than community reference parents (p<.001; Cohen's d=1.17). Moreover, we found that parents with high ADHD symptom severity reported higher parental stress than parents with low ADHD symptom severity (p<.001; d=0.39). In summary, we found evidence in support of the reliability and validity of the PSS, which overall was judged to be useful as a measure of parental stress in a Swedish context. In addition, our results underline the importance of considering parental stress and related needs in assessments and intervention planning involving families of children with NDCs.