This study intended to investigate misconceptions and errors commonly made by the students at primary level, finding out the reasons for these misconceptions and designing a remedial intervention for removing these misconceptions. The following research questions were developed to accomplish the task: • What are the misconceptions of students in learning mathematics at primary level? • What are the possible causes of these misconceptions of students in learning mathematics at primary level? • How can these misconceptions be rectified / removed? • How can teachers help the students to learn mathematics in a better way and remove the targeted misconceptions? The study was conducted in 12 sample schools and concepts included in the investigation were not limited to grade IV rather, all contents of mathematics were included from grade I to IV, excluding grade V. The grade V was excluded for the reason that the pre-test was administered in the beginning of the grade V study. The content tested through the pre-test was classified into eight concept areas namely, numbers, operations on numbers, fractions, operations on fractions, decimals, measurement, information handling and geometry. It was expected that the study would focus on misconceptions in few of these eight areas, but the findings of the pre-test and interviews with the teachers compelled the researcher to include all the eight areas as a significant number of misconceptions was found in all of the concept areas. The study was a mixed design approach (quantitative and qualitative). The pre-test and the post-test provided quantitative data while the interviews with the teachers and sample students helped to collect the qualitative data.On the basis of identification of the misconceptions and errors through the pre-tests, four students from each of the 12 schools were interviewed along with their teachers. The analysis of the qualitative and quantitative data provided insight about the causes of them is conceptions of students, and to remove these misconceptions a teachers training program was developed and conducted.At this stage, the study was converted into Pre test-intervention-post-test design keeping only one school out of the 12 schools as control group and the remaining 11 as the experimental group. Key misconceptions include numbers and operations on numbers; these were considered difficult by the students due to misconceptions regarding numbers’ names (language problem) and their place value. Fractions were thought as two numbers instead of part of a whole. Decimals were considered mostly on the basis of digits without having proper understanding of the place value of the digits written in a decimal number. Understanding of units for measuring different quantities was not entrenched due to not using measuring tools practically by the students. Mostly estimation of length, mass and area were made full of mistakes. Scale for drawing a graph,both line and bar graphs was not understood; it was seemed that students were having the wrong conception as they were not trained to draw a graph. Geometry was full of misconceptions starting from measuring a line segment or drawing a line segment of given measurement.The use of simple geometrical tools like protractor, straight edge, compass or set squares was felt difficult by most of the students and their teachers. The training of the teachers of the experimental group was focused on providing an opportunity to them to have an experience of doing mathematics as well as consolidating content including knowledge they were lacking.Misconceptions of the students in different concept areas were discussed with the teachers.The difference in gain scores of the experimental group students provided evidence that the students’ achievement improved in most of the concepts after being re taught by the experimental group teachers.