Abstract Background: Soil-transmitted helminths and Schistosoma spp are neglected tropical diseases causing parasites resulting millions of new infections and thousands of deaths every year in the Sub-Saharan Africa. The World Health Organization recommends certain anthelmintic drugs integrated with pure water, sanitation and hygiene and health education to control and eradicate soil-transmitted helminths and Schistosoma infections. However, efficacy of anthelmintic drugs is becoming a challenge now a days and still conclusive results are not yet attained regarding the cure and egg reduction rates of commonly prescribed anthelmintic drugs. Objective: The aim of this study was to assess the efficacy of re-dosing of single dose of mebendazole and praziquantel respective with STH and Schistosoma mansoni among Andasa primary school children in rural Bahir Dar, Northwest Ethiopia. Methods: This longitudinal study was conducted from February to May, 2018. Stool samples were collected and processed via Kato-Katz technique to determine parasite status and baseline egg counts. Single dose mebendazole and praziquantel were administered for children infected with Soil-transmitted helminths and Schistosoma mansoni, respectively following the laboratory results. After two weeks, a second round of stool samples was collected and re-dosing of single dose mebendazole and praziquantel were given for positive students. Third rounds of stool samples were collected after two weeks of redosing regimen. Following the third round stool examination, cure rate (CR) and egg reduction rate (ERR) were calculated. The data were analyzed using Statistical Packet for Social Science (SPSS) software version 20.0. The data were then summarized via descriptive statistical analysis. Results: A total of 422 students participated in this study. A re-dosed regimen of mebendazole achieved 100% CR and ERR treatment of Ascaris lumbricoides. The cure rate and egg reduction rate of mebendazole against hookworms were 90.5% and 98.7% respectively. On the other hand, the cure rate and egg reduction rate of single dose mebendazole against A.lumbricoides were 59.6% and 76.3%, respectively but the cure rate and egg reduction rate of single dose mebendazole against hookworms were 32.4% and 52.8%, respectively. The CR of Praziquantel (40mg/kg) against S.mansoni after single-dose and re-dose of Praziquantel treatment was 91.5% and 100%, respectively. The egg reduction rate of praziquantel after single and re-dose treatment was 95.1% and 100%, respectively Conclusion and recommendation: Single dose mebendazole showed reduced efficacy against Ascaris lumbricoides and hookworm infections. Re-dose treatment of mebendazole had satisfactory efficacy against hookworm and Ascaris lumbricoides infection. Single dose of praziquantel still had satisfactory efficacy against S.mansoni. Therefore, continuous evaluation of the cure rate of mebendazole against soil transmitted helminths should be done and the recommended dose should also be considered. Key words: Soil transmitted helminths, S.mansoni, mebendazole, Praziquantel, Andasa, Ethiopia.