Human fibrinogen (FIB) has been clinically proven to be considerably effective for the treatment of postoperative bleeding, with reported cases of allergic reactions to human FIB being rare. Here, we report a case of an anaphylactic shock in 27-year-old patients with rheumatic heart valve disease who received a human FIB infusion during mitral valve replacement, aortic valve replacement, and tricuspid valve-shaping surgery. The patients showed generalised profuse sweating, a barely noticeable skin rash, faint pulse, systolic pressure < 50 mmHg, and a heart rate of 71 beats/min. We share insights from a case of severe allergy to human FIB infusion during cardiac surgery, through which we have gained experience in the processes of diagnosing and treating. This report aims to provide a preliminary summary of the characteristics of this case to serve as a reference for fellow clinicians.