We show that using epitaxial strain and chemical pressure in orthorhombic YMnO3 and Co-substituted (YMn0.95 Co0.05 O 3) thin films, a ferromagnetic response can be gradually introduced and tuned. These results, together with the measured anisotropy of the magnetic response, indicate that the unexpected observation of ferromagnetism in orthorhombic o-RMnO3 (R=Y,Ho,Tb, etc.) films originates from strain-driven breaking of the fully compensated magnetic ordering by pushing magnetic moments away from the antiferromagnetic  axis. We show that the resulting canting angle and the subsequent ferromagnetic response, gradually increase (up to ∼1.2°) by compression of the unit cell. We will discuss the relevance of these findings, in connection to the magnetoelectric response of orthorhombic manganites. © 2010 American Institute of Physics.