Abstrak Penelitian ini bertujuan untuk mendeskripsikan kesalahan menyelesaikan soal-soal pecahan berdasarkan toksonomi bloom dan kemampuan awal siswa. Tujuan penelitian ini adalah (i) mendeskripsikan kesalahan konseptual dan prosedural dalam menyelesaikan soal-soal pecahan; Dan (ii) mendeskripsikan penyebab terjadinya kesalahan konseptual dan prosedural dalam menyelesaikan soal-soal pecahan. Hasil penelitian ini menunjukkan bahwa (i) kesalahan konseptual terjadi pada subjek berkemampuan tinggi dan sedang yaitu salah menggunakan, memanfaatkan, dan memilih prosedur atau operasi tertentu, salah mengaitkan berbagai konsep, salah mengklasifikasi objek-objek menurut sifat-sifat tertentu sesuai dengan konsepnya, dan salah menyatakan ulang sebuah konsep. Kesalahan prosedural yang terjadi pada subjek berkemampuan tinggi dan sedang yaitu salah menggunakan langkah-langkah dalam menyelesaikan soal-soal pecahan, salah memanipulasi langkah-langkah untuk menjawab suatu soal, melakukan penyimpulan tanpa alasan yang benar, serta salah dalam mencermati dan memahami petunjuk tes diagnostik (ii) penyebab terjadinya kesalahan yang dilakukan siswa antara lain adalah siswa kurang teliti membaca dan memahami maksud dari soal sehingga melakukaan kesalahan dalam menuliskan apa yang diketahui dan apa yang ditanyakan, siswa kurang memahami materi pecahan sehingga kurang mampu dalam menyelesaikan soal yang berkaitan dengan materi tersebut, daya ingat siswa terhadap rumus maupun pengertian-pengertian mengenai materi pecahan masih kurang sehingga siswa mengalami kesalahan dalam menyelesaikan soal-soal. Kata kunci: Analisis kesalahan, taksonomi bloom, kemampuan awal Abstract Concept in mathematics learning is the basic element that must be understood by students. The objectives of the research are to describe (i) conceptual and procedural mistakes in solving fractions questions; and (ii) the cause of conceptual and procedural mistakes in solving fractions questions.The results of the research showed that (i) conceptual mistakes occurred to high and medium ability subjects, namely mistake in connecting various concepts, mistake in classifying certain objects according to certain characters based on the concept, and mistake in restating a concept. Procedural mistakes occurred to high and medium ability subjects, namely mistake in using stages in solving fractions questions, mistake in manipulating stages in solving fractions questions, mistake in manipulating stages to answer a question, drawing conclusion without the right reason, and mistake in observing and understanding diagnostic test instructions, namely students did not continue solving stage; (ii) the causes of the mistakes which were conducted by the students were: students did not read carefully and lack of comprehension of the questions so they conducted mistake in writing what had been understood and being questioned, students had lacked of understanding the meaning of what was asked in the question so they conducted mistake in writing the final answer according to what was stated in the question, the students had lacked of understanding in fraction material so they were less’ able in understanding on fractions material were low so they had mistakes in solving the questions.