Kleijnen served as a referee for the following journals (listed alphabetically); some journals no longer exist (e.g. Excerpta Informatica):
AIChE Journal
American Institute of Aeronautics and Astronautics (AIAA) Journal
American Journal of Mathematical and Management Sciences
American Society of Mechanical Engineers (ASME) Journal of Mechanical Design
Annals of Operations Research
Applied Energy
Applied Mathematical Modelling
Applied Soft Computing
Biometrika
Central European Journal of Operations Research
Chemical Engineering Journal
Communications of the ACM
Communications in Statistics
Complexity
Computers and Electronics in Agriculture
Computers & Chemical Engineering
Computers & Industrial Engineering
Computer Physics Communications
Computers in Industry
Defence Technology
Engineering with Computers
Environmental Modelling & Software
Environmental Monitoring and Assessment
European Journal of Industrial Engineering
European Journal of Operational Research
Excerpta Informatica
Expert Systems
Expert Systems With Applications
IEEE Transactions on Systems, Man, and Cybernetics--Part A: Systems and Humans
IIE Transactions
INFORMS Journal of Computing
International Journal of Computational Methods
International Journal of Computer Integrated Manufacturing
International Journal of Engineering Systems Modelling and Simulation
International Journal of Modelling & Simulation
International Journal of Production Research
International Journal of Simulation and Process Modelling
Iranian Journal of Science and Technology; Transactions A: Science
Journal of the ACM
Journal of the American Statistical Association
Journal of Applied Mathematics
Journal of Computational Science
Journal of Engineering Manufacture
Journal of Global Optimization
Journal of Mechanical Design
Journal of Quality Technology
Latin American Journal of Solids and Structures
Management Science
Mathematical and Computer Modelling
Mathematical and Computer Modelling of Dynamical Systems
Mathematical Problems in Engineering
Military Operations Research Society Journal
OR Spectrum
Operations Research
Production Planning and Control
Reliability Engineering & System Safety (RESS)
Risk, Energy Risk, Insurance Risk
Scandinavian Journal of Statistics
SIAM Journal on Optimization
Simulation
Simulation Modelling Practice and Theory
Simulation: Transactions of the Society for Modeling and Simulation International
SN Applied Sciences
Statistica Neerlandica
Computers & Operations Research
Chemical Reviews
Computers @ Structures
System Dynamics Review
Technometrics
The Annals of Applied Statistics
Transactions on Modeling and Computer Simulation (TOMACS)
Transactions on Systems, Man, and Cybernetics
Turkish Journal of Electrical Engineering & Computer Sciences