The analysis of the unexpected ionospheric phases before large earthquakes is one of the cutting-edge issues in earthquake prediction studies. In this study, the total electron content (TEC) data from seven International GNSS Service (IGS) stations and the global ionosphere maps (GIMs) were used. Short-time Fourier transform (STFT) and a running median process were applied to the TEC time series to detect abnormalities before the Mw 7.3 Iran–Iraq border earthquake on 12 November 2017. The analyses showed positive anomalies 8–9 d before the earthquake and some positive and negative anomalies 1–6 d before the earthquake. These anomalies were cross-checked using the Kp, Dst, F10.7, Bz component of the interplanetary magnetic field (IMF Bz), electric field (Ey), and plasma speed (VSW) space weather indices. The results showed that the anomalies 1–6 d before the earthquake were caused by a moderate magnetic storm. Moreover, the positive anomalies 8–9 d before the earthquake were likely related to the Iran–Iraq border earthquake due to quiet space weather, local dispersion, and the proximity to the epicenter.