The West Florida Shelf (WFS) is a source of uncertainty for the Gulf of Mexico carbon budget. Data from the synthesis of approximately 135,000 pCO₂ values from 97 cruises from the WFS show that the shelf waters fluctuate between being a weak source to a weak sink of carbon. Overall, the shelf acts as a weak source of CO₂ at 0.32 ± 1.5 mol m⁻² yr⁻¹. Subregions, however, reveal slightly different trends, where surface waters associated with 40–200-m isobath in the northern and southern WFS are generally weak sinks all year, except for summer when they act as sources of CO₂. Conversely, nearshore waters (<40 m) are a source of CO₂, particularly the southern shallow waters, which are a source all year round. The pCO₂ of seawater has been increasing at a rate of approximately 4.37 μatm/year as compared to atmospheric pCO₂ which has increased at a rate of about 1.7 μatm per year from 1996 to 2016. The annual CO₂ flux has increased from −0.78 to 0.92 mol m⁻² yr⁻¹ on the shelf from 1996–2016. The WFS is emitting 9.23 Tg C/year, with the southern nearshore region emitting the most at 9.01 Tg C/year and the northern region acting as a sink of −1.96 Tg C/year. Aragonite saturation state on the WFS shows seasonal and geographic trends with values ranging from 2 to 5. Lowest values are found in winter associated with subregion <40-m isobath.