Abstract Background To investigate the relationships of monocyte to high-density lipoprotein cholesterol (HDL-C) ratio (MHR) with left ventricular hypertrophy (LVH) in young and middle-aged patients with essential hypertension (EH). Methods A retrospective analysis was performed on clinical data of 294 young and middle-aged patients with EH (aged from 18 to 65 years old). According to the left ventricular mass index (LVMI), the patients were divided into LVH (n = 98) and non-LVH (n = 196) groups. The data on echocardiography, routine blood test, biochemical examination, and so on were collected in all subjects, then LVMI and MHR were calculated. The association between MHR and hypertensive LVH was analyzed by correlation and binary logistic regression analyses. The receiver operating characteristic curve (ROC) was used to determine the predict value of MHR. Results MHR was higher while HDL-C was lower in the LVH group compared with the non-LVH group (MHR: 0.47 ± 0.11 vs. 0.33 ± 0.12, P < 0.001; HDL-C: 1.05 [0.94–1.22] vs. 1.27 [1.07–1.47] mmol/l, P < 0.001). Correlation analysis showed that LVMI was positively correlated with MHR (r = 0.381, P < 0.001). Multivariate logistic regression analysis showed that MHR was an independent risk factor for LVH in young and middle-aged EH patients (odds ratio = 2.914, 95% confidence interval [CI] 2.084–4.068, P < 0.001) after adjusting for body mass index, smoking, HDL-C, and other confounding factors. The area under the ROC curve of MHR for predict LVH was 0.831 (95% CI 0.782–0.880), and the optimal cutoff value of MHR was 0.37, with a sensitivity of 93.9% and a specificity of 75.5%. Conclusions MHR is positively correlated with LVH in young and middle-aged patients with EH. MHR is an independent risk factor for LVH in this population, and can be used for LVH risk screening.