Chloroaluminum phthalocyanine (ClAlPc) thin films, vacuum sublimed on SnO2-covered glass substrates, were exposed to KCl solutions of various pH values (from 2.0 to 8.0) in the fluid cell of an atomic force microscope (AFM). The evolution of the surface morphology of the film was followed in situ. Complementary experiments on the film morphology were also performed by scanning electron microscopy. The chemical evolution of the film surface was obtained by time-of-flight secondary ion mass spectrometry. On the one hand, when ClAlPc is immersed in KCl solutions at pH = 2.0 or 3.0, a slow dissolution of the outermost surface of the film occurs. This is followed by the hydrolysis of ClAlPc in solution to form first the hydroxyaluminum phthalocyanine (HOAlPc) and then the mu-oxo-dimer, PcAlOAlPc. The latter recrystallizes as long needles on top of the initial film, thereby changing drastically its surface morphology. On the ether hand, when ClAlPc is immersed in KCl solutions at pH = 5.7 or 8.0, the hydrolysis of ClAlPc occurs at the surface of the film without noticeable morphological modifications. A subsequent immersion of the film in KCl at pH = 2.0 may have the same effect on the film morphology as the one previously described for pH = 2.0 or 3.0, as long as mechanical energy is provided to the film, either by ultrasound or by the cantilever tip of the AFM. When the latter is involved, the source of mechanical energy is localized in space and patterning of the surface morphology becomes possible.