The clinical significance of papillary muscle hypertrophy and its electrocardiography (ECG) findings has not been fully elucidated. This study aimed to investigate the relationship between ECG findings and papillary muscle hypertrophy and to confirm the importance of papillary muscle measurements on transthoracic echocardiography (TTE). Of the 237 consecutive patients who showed left ventricular hypertrophy (LVH) pattern on a 12-lead ECG, TTE data were available for 101 patients. The patients were divided into the two groups according to the presence (ECG-LVH [strain pos] group, n = 60) or absence (ECG-LVH [strain neg] group, n = 41) of LV strain pattern (study 1). The prevalence of papillary muscle hypertrophy using TTE was significantly higher in the ECG-LVH (strain neg) group than in the ECG-LVH (strain pos) group (P = .0002). Of the 42 cases with papillary muscle hypertrophy, 5 cases (12%) showed isolated papillary muscle hypertrophy with normal geometry. ECG data were prospectively analyzed for 36 patients who were diagnosed with papillary muscle hypertrophy by TTE (study 2). The prevalence of LV strain pattern was significantly higher in patients with LV wall hypertrophy than in those without LV wall hypertrophy (P = .04). Of the 25 cases with papillary muscle hypertrophy, 6 cases (24%) showed normal geometry and 4 cases (16%) showed ECG abnormality. Isolated papillary muscle hypertrophy can cause ECG abnormalities such as LV high voltage and LV strain pattern. Particular attention must be paid to the papillary muscle during echocardiographic examinations.