Mineral scale is the hard inorganic solid deposited from aqueous solution due to local supersaturation. Scaling issue is one of the most serious water-related operational problems in various industries, especially in oilfield operations. Scale deposition can cause production downtime and pose severe threats to the personnel safety and operational integrity. Composite scales are the scale particles composed of multiple mineral phases. While extensive efforts have been made to investigate the behaviors of precipitation and formation of single scale, knowledge of thermodynamics and kinetics of composite scales is still very limited. The presence of scaling ions would accelerate the kinetics of cocrystallization and coprecipitation of composite scales since these ionic species might provide the seeding points for nucleation. The information presented in this chapter suggests that scale formation behaviors solely from experimental and computational data on pure scale formation process might incorrectly estimate the severity of composite scaling which commonly takes place at actual operational conditions. Although the difference in scaling propensity between composite fouling and single scale has been proved to exist, efficient control strategy specifically designated to manage composite scale is very limited and future studies are required on this regard. Nevertheless, based on the elaboration in this Chapter, a number of experimental efforts have been reported to address scaling threat associated with composite scales. The review in this chapter provides comprehensive and informative details on the thermodynamics and kinetics of several common composite scales.