In order to study the gas exchange, activity of photosynthetic enzymes and growth at leaves and whole coffee plant Coffea arabica L., under CO₂ increase in the air [375 mmol (CO₂) mol (air)^-1 (control); 375+200 mmol (CO₂) mol (air)^-1 and 375+400 mmol (CO₂) mol (air)^-1], the plants were growing in pots into the open top chambers for six months. Whole plant gas exchange was measured under semi-controlled conditions in a chamber. The plant growth variables as height of the plant, stem diameter, number of branches, knots and leaves, and dry weight accumulated in the organs include roots, and leaf area were measured, as well as the variables related with the biochemical photosynthetic as chlorophylls, proteins, and the activity of Rubisco, PEPC and Glycolate oxidase. The statistical analysis reflected significant differences in all the variables evaluated under an atmosphere enriched with CO₂ with respect to the control, mainly in the treatment with 375+400 mmol (CO₂) mol (air)^-1. The increased activity of Rubisco and Glycolate Oxidase enzymes, were related with the treatments and explain the behavior of the canopy photosynthesis. At the end of the experiment the plant growth variables measured were similar for the three treatments, which suggest the acclimatization of plants to high environmental concentrations of CO₂ over the course of time.