The purpose of this explorative study is to investigate how primary school students benefit from intervention focusing on learning science phenomena with multiple online sources. Multiple online sources offer a good possibility to learn complex science phenomena (e.g., Brand-Gruwel & van Strien 2018). Even young children are expected to use the internet environment in school assignments to find multiple sources and to write their synthesis based on relevant sources. The participants (N=44) were 11–12 years old. The intervention study was conducted in an authentic primary school classroom and was a part of normal school work. The study followed pre- and post-test design and was designed as a project in science class. The topic was “decline of insect population” and lasted five lessons. The results indicate that the intervention had a positive effect on acquisition of multiple source skills and conceptual knowledge. It can be suggested that multiple text comprehension skills cannot be viewed separately from reading skills. In order to support online inquiry skills, we need explicit teaching of different aspects of multiple source writing also in science.