The purpose of this study is to evaluate the performance of a sequential multi-modality imaging algorithm for diagnosing acute appendicitis in pregnancy. This IRB-approved, HIPAA compliant study included 127 consecutive pregnant patients imaged for suspected appendicitis between October 2007 and May 2012; all patients initially underwent ultrasound (US) examination, followed by magnetic resonance imaging (MRI) if results of US were negative or equivocal. Computerized tomography (CT) was reserved for cases with inconclusive US and MRI results. The EMR was reviewed, recording results of imaging examinations and clinical outcomes. The diagnostic performance of this sequential multi-modality imaging algorithm was calculated with pathology correlation. Two (1.9 %) of the 127 US examinations reported suspected appendicitis; 125 (98.4 %) were inconclusive. Of the 125 patients with inconclusive US examinations, 103 underwent MRI, of which eight (6.2 %) demonstrated findings of acute appendicitis. Of the 103 patients that received MRI, nine (8.7 %) underwent CT. One patient had a CT performed directly after an inconclusive US exam. No additional cases of appendicitis were detected with CT. The sensitivity and specificity of US alone was 12.5 and 99.2 %, respectively; MRI was 100 and 93.6 %; the sequential multi-modality modality algorithm including US, CT, and MRI was 100 and 98.3 %. The diagnostic performance of this sequential multi-modality imaging algorithm for diagnosing acute appendicitis in pregnancy is high. Given the low yield of US, MRI should be considered the first-line imaging test. Although CT was employed in a small fraction of inconclusive MRI examinations, it still has a role in the diagnostic work-up of the pregnant patient with suspected appendicitis.