Abstract: Oscillating-amplifying integrated fiber lasers (OAIFLs) have emerged as a promising technology in high-power laser applications by combining the structural simplicity and superior anti-reflection capability of oscillators with the high efficiency of amplifiers. This review systematically summarizes recent progress from both theoretical and experimental perspectives. Theoretically, the focus is on advances in modeling mode instability and nonlinear effects, aiming to provide optimization guidelines for achieving high-power output. Experimentally, OAIFLs have successfully realized kilowatt-level narrow-linewidth and 10-kW-class broadband laser output in conventional wavelength bands. Beyond these bands, research primarily targets 1050 nm and 1018 nm fiber lasers. Furthermore, innovative dual-end output designs address core high-power challenges through distributed power extraction, significantly enhancing system power scalability. These advancements will accelerate broader applications in industrial processing, biomedical fields, and national defense. Analysis of current trends highlights key evolutionary pathways: benefiting from the integrated structure’s unique advantages in nonlinear management and amplified spontaneous emission (ASE) suppression, operational wavelengths are expanding from the conventional 1050–1080 nm range toward shorter specialty bands; driven by demands in coherent beam combining and high-precision spectroscopy for high-brightness sources, output spectra are shifting from broadband to narrow-linewidth emission; gain media are evolving from conventional homogeneous fibers to specially designed geometric structures to simultaneously mitigate nonlinear effects and transverse mode instability (TMI) under high-power conditions; to meet needs in precision machining, spectroscopic sensing, and scientific research for lasers with high peak power and tailored temporal profiles, operational modes are diversifying from continuous-wave to varied pulsed regimes; and output configurations are advancing from simple single-end to sophisticated dual-end designs, effectively addressing key challenges in high-power laser delivery. Nevertheless, persistent limitations include insufficient universality of theoretical models and a lack of systematic experimental validation. Future research should emphasize two complementary dimensions. Theoretically, efforts must deepen model construction and mechanistic analysis—including refining temporal modeling, investigating TMI origins and nonlinear coupling mechanisms, and elucidating the physics of pump-timing-independent operation. Experimentally, the focus should be on continuously optimizing output performance—enhancing power and efficiency, improving spectral characteristics and beam quality, and advancing toward pulsed and supercontinuum generation capabilities.