Introduction: Available data imply that extent of resection (EOR) improves progression free survival (PFS) in patients harboring a low-grade glioma (LGG). Intraoperative high-field magnetic resonance imaging (iMRI) is an established diagnostic tool that can detect residual tumors in LGG surgery. We conducted a retrospective study to evaluate the extent of resection, clinical outcome and PFS in conventional and iMRI-based LGG resection. Patients and methods: A total of 69 patients was assessed. Only World Health Organization (WHO) grade II LGGs were evaluated. Thirty-three patients had surgery using iMRI (2008–2013). Thirty-six patients underwent surgery before introduction of iMRI at our center (2000–2008). Demographic data, extent of resection (EOR), complication rate, overall time of surgery and progression free survival were evaluated. Results: The majority of patients were treated for a diffuse astrocytoma in both cohorts (iMRI: 46.9%, historical (hist.): 61.1%). Extent of resection was a positive prognostic factor for longer PFS according to Cox regression multivariate analysis controlled by eloquent location, tumor recurrence and histological subtype [P<0.001, hazard ratio (HR) 0.247]. Additionally, the Cox regression showed the advantage and longer PFS of iMRI-assisted resections using the same settings (P=0.038, HR=0.378). Permanent neurological deficits (PND) after surgery were found in 12.5% (n=4) of the iMRI group and in 22.2% (n=8) of the historical group. Duration of surgery was significantly higher in the iMRI group (iMRI: 6.3 h, hist.: 4.3 h, P<0.036). However, there was no significant increase of postoperative surgical complications. Gross total resection (GTR) was achieved in 63.6% (n=21) of iMRI patients and 27.8% (n=10, P<0.0069) in the historical control, respectively. Binary logistic regression showed that iMRI has a significant impact on tumor remnants (P<0.001). Conclusion: In our study we have confirmed EOR to be an important positive prognostic factor for PFS. At our center, compared to a historical group, the routine use of iMRI increases EOR and was associated with a decrease in complications. Due to a selection bias no final conclusion can be drawn as to whether the use of iMRI increases PFS.