The G4 received mixed to positive reviews; while praising the G4's display quality, camera, and overall performance, critics characterized the G4 as being a robust device that did not contain enough substantial changes or innovation over its predecessor to make the device stand out against its major competitors, but could appeal to power users needing a smartphone with expandable storage and a removable battery due to the exclusion of these features from its main competitor on launch, the Samsung Galaxy S6.

[6][7] The device also became the subject of criticism due to instances of hardware failure caused by manufacturing defects, deemed "bootloops", which culminated in a class-action lawsuit filed in March 2017.

[7] The camera software was upgraded with raw image support, along with a new manual mode offering the ability to adjust the focus, shutter speed, ISO and white balance.

[17][18] It enables new features such as "Google Now on Tap", which allows users to perform searches within the context of information currently being displayed on-screen, and "Doze", which optimizes battery usage when the device is not being physically handled.

The Verge felt that the G4 could appeal to power users alienated by the removal of expandable storage and replaceable batteries on the then-recently released Samsung Galaxy S6.

The G4's rear camera was praised for its quality and color reproduction, along with its "comprehensive" manual mode and its "uncommon" ability to save raw images, but it was noted that its autofocus sometimes missed focus or took long to achieve focus, and that the manual mode did not offer saturation or sharpness controls.

"[7] Some users reported inconsistencies in the performance of the G4's touchscreen, with some units—particularly U.S. T-Mobile and Verizon variants—having problems registering quick taps and swipes.

[21][22][23] In January 2016, LG confirmed that some G4 units had a manufacturing defect that eventually caused them to enter an unrecoverable reboot loop, resulting from "loose contact between components".