Celery (Apium graveolens var. dulce) is affected by several plant diseases, such as Fusarium oxysporum f. sp. apii (Foa). Four Foa races have been found in the US. The goals of this study were to determine which races are present in Costa Rica and to quantify the tolerance of the imported commercial cultivars of celery produced in the country. Isolates from 125 symptomatic celery plants from three different geographical locations were analyzed, 65 of which were selected for phylogenetic analysis. All isolates presented a short sequence of five nucleotides that differentiates Foa race 3 in the IGS rDNA region. Three different haplotypes closely related to race 3 were found, which were highly virulent, produced great losses, and affected all cultivars (resistant to races 2 and 4) of imported commercial celery. Additionally, five different cultivars of celery were evaluated against seven pathogen isolates identified as race 3 in greenhouse conditions. Two of the cultivars showed significantly less chlorosis, wilting, mortality, and higher fresh weight. Most of the Foa isolates significantly increased chlorosis, wilting, and mortality compared to non-inoculated control. Celery producers in Costa Rica lack access to seeds resistant to the Foa race 3 present in the country.