The current study explores the effectiveness of involving students in environmental science projects for their environmental knowledge and attitudes towards science. The study design is a quasi-experimental pre-post control group design. The sample was 62 11th-grade female students studying at a public school in Oman. The sample was divided into two groups: an experimental group (N = 34) which conducted five different environmental-based projects for two months and a control group (N = 28) which studied using the traditional methods. For the purpose of study, two instruments were designed: the Environmental Knowledge Test (EKT) and the Science Attitudes Survey (SAS). The results indicated that students' involvement in environmental projects had a statistically significant positive impact on their environmental knowledge and science attitudes. The experimental group significantly outperformed the control group in both instruments. The results also indicated that the projects that made the most impact were those that required students to produce enjoyable and unusual final products such as a documentary movie, a school-wide campaign, and school-wide environmental exhibit. This promising result is what distinguishes the current study: that PBL could be implemented with few resources, inside the school building and within the assigned time by the official teacher guide for the undertaken topics.