To expedite the discovery of novel molluscicides in the laboratory, this study aimed to evaluate the performance of a new molluscicidal assay. This assay is based on Oncomelania hupensis quadrasi snails and is called miniaturized plate test or mpt. To perform this assay, a 12-well plate, 3 snails per well, and 24-h exposure period were used. The performance of mpt was evaluated using niclosamide and Ardisia plant extract (tagpo extract) as test substances while WHO’s guidelines for a conventional plate test (cpt) served as standard. One cpt and four mpt independent trials were performed for niclosamide and tagpo extract. Probit analysis of dose–response data was run in R to generate lethal concentrations (LC50 and LC90), while lethal ratio test was performed to detect significant difference between paired LC50s (or LC90s). Using niclosamide, the calculated LC50 values were 0.104, 0.127, 0.136, 0.139, and 0.140 g/m2 for cpt, mpt 1, mpt 2, mpt 3, and mpt 4, respectively, while the LC90 values were 0.266, 0.268, 0.244, 0.251, and 0.261 g/m2, using the same sequence, respectively. For tagpo extract, the LC50 values were 1.467, 1.547, 1.659, 1.797, and 1.659 g/m2, for cpt, mpt 1, mpt 2, mpt 3, and mpt 4, respectively, and the LC90s were 2.188, 2.195, 2.501, 2.358, and 2.501 g/m2, respectively. The lethal ratio test revealed that a significant difference exists between the LC50s of cpt and mpt 1 when using niclosamide with a lethal ratio and confidence limits of 0.820 (0.663, 0.977, p