Undoped and Mn-doped (5 and 10 at.%) monoclinic CuO nanoflakes are synthesized by wet chemical method. Undoped CuO nanoflakes exhibit room temperature ferromagnetism (RTFM) due to the uncompensated surface spins originating mainly from the defects and oxygen vacancies on the surface. But Mn-doped CuO nanoflakes do not show RTFM, which is due to the formation of Mn clusters on the surface. FTIR analysis shows that the number of defects, which has significant influence on both the magnetic and ethanol sensing properties is more in undoped CuO than in Mn-doped CuO. The ethanol sensing studies show that CuO is more sensitive to ethanol compared with Mn-doped (10 at.%) CuO, which reveals that the sample showing RTFM also shows more ethanol sensitivity compared with the sample that does not show RTFM. The results also reveal that the nature of the sample surface plays a significant role in both the magnetism and the sensing mechanism. (c) 2013 Elsevier B.V. All rights reserved.