Peroxisomes are eukaryotic organelles that support several metabolic pathways critical to survival and development. These pathways include diverse oxidative reactions with harmful reactive byproducts that are neutralized with enzymes accumulated in peroxisomes. New peroxisomes can be generated via de novo formation from the endoplasmic reticulum or growth and fission of mature peroxisomes with the assistance of proteins called peroxins (PEX proteins). Once formed, peroxisomes acquire necessary enzymes by using other peroxins to import lumenal proteins. Although we have a general framework for understanding peroxisome biogenesis, we lack a complete molecular understanding of the activity and specific sequence of events through which these peroxins function. Unlike in mammals, -oxidation is exclusively peroxisomal in plants, making plants an ideal multicellular system in which to study peroxisomes and peroxisomal metabolism. Germinating Arabidopsis seedlings rely on peroxisomes to catabolize fatty acids stored in lipid droplets, and mutations in peroxin genes confer a range of easily assayed developmental defects that report peroxisome function. I elucidated molecular mechanisms underlying Arabidopsis peroxisomal biogenesis and function by characterizing peroxin mutants and peroxin mutant suppressors. These suppressors carry secondary mutations that restore peroxisomal function to Arabidopsis peroxin mutants. I examined suppressors of pex10-2 and pex12-1, mutants defective in ubiquitin-protein ligases that aid in peroxisome receptor recycling, and pex14-1 and pex14-6, mutants defective in a docking complex peroxin that aids in peroxisomal protein import. I clarified details of how these peroxins function and uncovered novel associations between peroxins by assessing the steps in peroxisomal function that are restored in the suppressors. One pex14-6 suppressor corrects the splicing defect of the original lesion, and I used it to investigate how splicing factors maintain splicing fidelity. One pex12-1 suppressor is defective in a peroxin implicated in peroxisomal membrane protein insertion and pre-peroxisome budding from the endoplasmic reticulum, and I used it to investigate a potential role in protein import. Finally, I examined the role of PEX16, an early-acting peroxisome biogenesis factor, in plants. Together, these studies revealed varying methods for modulating peroxisome function and suggest additional obscure factors in peroxisome competence.