The LRRK2 G2019S mutation is found at higher frequency among Parkinson disease (PD) patients of Ashkenazi Jewish (AJ) ancestry. This study was designed to test whether an internet-based approach could be an effective approach to screen and identify mutation carriers. Individuals with and without PD of AJ ancestry were recruited and consented through an internet-based study website. An algorithm was applied to a series of screening questions to identify individuals at increased risk to carry the LRRK2 G2019S mutation. About 1000 individuals completed the initial screening. Around 741 qualified for mutation testing and 650 were tested. Seventy-two individuals carried at least one LRRK2 G2019S mutation; 38 with PD (12.5%) and 34 without (10.1%). Among the AJ PD participants, each affected first-degree relative increased the likelihood the individual was LRRK2+ [OR = 4.7; 95% confidence interval = (2.4–9.0)]. The same was not observed among the unaffected AJ subjects (P = 0.11). An internet-based approach successfully screened large numbers of individuals to identify those with risk factors increasing the likelihood that they carried a LRRK2 G2019S mutation. A similar approach could be implemented in other disorders to identify individuals for clinical trials, biomarker analyses and other types of research studies.