Porcine circovirus type 3 (PCV3) is a disease associated with porcine dermatitis and nephrotic syndrome (PDNS) that has caused significant economic losses to swine herds since its discovery in 2016. To develop a simple, on-site, rapid, and sensitive assay to combat the spread of PCV3, we optimized the CRISPR/Cas12a (also known as Cpf1) system combined with enzymatic recombinase amplification (ERA) nucleic acid amplification to diagnose PCV3. The results showed that the ERA-CRISPR/Cas12a reaction could detect PCV3 within 1 h in genomic DNA harboring a minimum of seven copies. Additionally, we confirmed no cross-reactivity with PCV2, PCV4, or other porcine viruses, revealing the good specificity of this technique. These results demonstrated the ability of ERA-CRISPR/Cas12a to detect DNA at the single-molecule level and provide a rapid, simple, ultrasensitive, one-pot point-of-care test for PCV3 and suggest its potential for a variety of nucleic acid detection applications.