The series of conjugated polymers having stimuli-responsive luminescent properties are reviewed. Initially, polarity-sensitive materials are surveyed. Basically, emission color changes can be explained by solvatochromic luminescent properties. In some cases, aggregation is a key phenomenon for detecting polarity changes. From this viewpoint, recent works on the development of luminescent sensors based on aggregation-induced emission properties are introduced. Next, sensing materials for evaluating environmental factors, detecting target molecules, and monitoring chemical reactions or external stimuli are illustrated. Mechanisms and results will be illustrated.