In this work barium sulfate precipitation is studied in a tubular reactor in a wide range of operating conditions. The effect of reactant concentrations and barium or sulfate excess on crystal-size distribution and morphology is investigated. Experimental results show that ion excess has a strong influence and that at high concentration aggregation takes place. Computational fluid dynamics is coupled with the finite-mode probability density function approach for taking into account both macro- and micromixing, whereas the population balance is treated by using the standard moment method. Comparison with experimental data suggests that when micromixing and agglomeration are properly taken into account, the agreement is improved. However, this statement is partially affected by the lack of knowledge in barium sulfate kinetics.