The Trends in International Mathematics and Science Study (TIMSS) is one of the most influential assessments of student achievement conducted at regular interval every four years. It provides reliable data about the mathematics and science achievement of students in grade 4 and grade 8, as well as data that informs instruction, curriculum development and teaching-learning process. Curriculum related factors are among the most prominent elements that affect TIMSS results. This study explores the impact of recent revisions in the school mathematics curriculum implemented by the Ministry of Education in Bahrain (The Bahrain Numeracy Strategy) on the TIMSS achievement results. The analysis focuses on the three cognitive domains (Knowing, Applying & Reasoning) as well as the three content domains (Number, Geometric Shapes and Measurement & Data Analysis) among fourth grade students. A thorough review of the curriculum and structured interviews and reflections with in-service teachers who witnessed a prominent change in the outcome revealed that Bahraini students' scores improved in all three content domains while comparing 2011 and 2015. The possible explanations and reasons for those changes in achievement are further discussed.