Berdasarkan pengamatan terhadap aktivitas kelas dan pencapaian belajar dalam mata kuliah Matematika, ditemukan bahwa seluruh mahasiswa (100%) mengalami kesulitan dalam menyelesaikan masalah. Kesulitan ini perlu segera diatasi, mengingat pentingnya keterampilan pemecahan masalah dalam mempersiapkan mahasiswa menghadapi dunia kerja. Oleh karena itu, langkah-langkah yang diambil melalui penelitian dan pengembangan mencakup pembuatan buku ajar matematika teknik mesin berbasis problem solving yang memenuhi kriteria validitas dan kepraktisan. Pengembangan buku ajar ini menggunakan metode penelitian design research dengan jenis development study yang meliputi tahap preliminary, perencanaan, evaluasi formatif, dan prototyping. Berdasarkan hasil review dari para ahli, buku ajar ini dinilai sangat valid. Secara bersamaan, buku ajar diuji coba pada lima mahasiswa untuk menilai keterbacaannya, dan hasilnya menunjukkan bahwa buku ajar tersebut tergolong sangat praktis. Hasil uji coba one-to-one mengungkapkan bahwa penerapan langkah-langkah pemecahan masalah yang sistematis, seperti memahami masalah, merancang rencana, melaksanakan rencana, dan mengevaluasi kembali, membantu mahasiswa mencapai solusi yang lebih tepat. Temuan juga menunjukkan bahwa penerapan langkah-langkah tersebut meningkatkan rasa percaya diri mahasiswa dalam menyelesaikan masalah. Dengan demikian, buku ajar ini memenuhi standar validitas dan kepraktisan.Based on observations of classroom activities and learning outcomes in the Mathematics course, it was found that all students (100%) experienced difficulties in problem-solving. Given the importance of problem-solving skills in preparing students for the workforce, this issue must be addressed promptly. Therefore, the steps taken through research and development involved creating a mathematics textbook for mechanical engineering based on problem-solving that meets the criteria of validity and practicality. The development of this textbook employed a design research method with a development study approach, including several stages: preliminary, planning, formative evaluation, and prototyping. Based on expert reviews, it was concluded that the developed textbook is highly valid. Simultaneously, the textbook was tested with five students to assess its readability, and the results showed that it was efficient. The results from the one-to-one trial revealed that applying systematic problem-solving steps, such as understanding the problem, devising a plan, carrying out the plan, and looking back, helped students arrive at more accurate solutions. Other findings also indicated that following these steps increased students’ confidence in solving problems. Therefore, it can be concluded that the mathematics textbook for mechanical engineering based on problem-solving meets the standards of validity and practicality.