Pharmacogenetics brought the promise of matching individuals with treatments that would be efficacious while minimizing adverse events. This has been long needed in psychiatry, where treatment options have been empirical and treatment choices have been made largely based on clinical judgment. The efficacy and tolerability of antidepressants, the most common drugs used in mood disorders, have been widely studied in pharmacogenetics. Genetic association studies have been reported for pharmacokinetic genes such as the CYP450 isoenzymes or MDR1, and pharmacodynamic genes such as the serotonin transporter (SLC6A4) or the serotonin 2A receptor (HTR2A). However, despite the large number of reports, clinically useful predictors are still scarce for antidepressant monotherapy. Pharmacogenetic predictors of efficacy for mood stabilizers such as lithium and anticonvulsants have not had a dissimilar fate, and clinically meaningful markers are yet to emerge. The lack of consistent results may be in part due to small samples of heterogeneous populations and lack of consensus on phenotype definitions. Current pharmacogenetic recommendations include testing for HLA-B*1502 when using carbamazepine in Asian ancestry populations to prevent Stevens–Johnson syndrome, CYP2D6 genotypes when using pimozide, and CYP2D6 in polypharmacy to minimize drug interactions. This review, which is aimed at clinicians, lays the basis for understanding strengths and weaknesses of pharmacogenetic studies and outlines current clinical uses of these biomarkers.