Indoor air quality (IAQ) plays a critical role in occupant health, comfort, and cognitive performance, yet many university offices struggle to maintain optimal conditions despite advanced ventilation systems. This two‐year crossover study evaluated whether introducing common indoor plants could supplement mechanical ventilation to improve IAQ in two comparable administrative offices. Sixty‐eight healthy adult staff members (mean age 37 ± 3 years) were assigned to work in a 1,765 ft² office either with 30 Epipremnum aureum plants or without greenery during 2020, then swapped offices in 2021. Over each condition, 24 eight-hour measurements of CO₂, PM₂.₅, total volatile organic compounds (TVOCs), temperature, and relative humidity were recorded. Between‐group analyses revealed that offices with plants exhibited significantly lower mean CO₂ concentrations (912 ± 321 ppm vs. 1,343 ± 745 ppm; p < 0.01) and PM₂.₅ levels (6.8 ± 3.1 µg/m³ vs. 9.5 ± 4.2 µg/m³; p = 0.03) compared to unplanted offices. Paired comparisons within participants confirmed these reductions (CO₂: 899 ± 307 ppm vs. 1 498 ± 692 ppm, p < 0.01; PM₂.₅: 5.6 ± 2.9 µg/m³ vs. 10.7 ± 6.3 µg/m³, p < 0.01). No significant differences were found for TVOCs, temperature, or humidity. These findings demonstrate that modest plantings can yield substantial gains in air freshness and particulate removal, offering a low‐cost, biophilic strategy to enhance IAQ in university workspaces. Incorporating indoor plants alongside standard HVAC maintenance may, therefore, help safeguard staff well-being and productivity, particularly in older or high-density buildings where upgrading mechanical systems is impractical.