Advances of alpine timberline forests during last century are not ubiquitous worldwide, suggesting additional factors and mechanisms likely affect the response of alpine timberline forests to climate warming. Upward shifts of treelines begin with seed dispersal and germination, and seedling establishment above the treeline and any limiting factors during these processes may affect treeline migration. Therefore, investigation of mechanisms controlling seedling recruitment at alpine treeline will be helpful to elucidate treeline formation and its response to future climate change. We reviewed recent advances in tree seedling recruitment at alpine treelines from the key seed and seedling stages. For the seed stage, the seed quantity and quality generally decreased with the sum temperature during summer; the seed dispersal to elevations above treeline was impeded by low wind speed, dense dwarf shrub and grass cover; the ability of seed germination above the treeline was impaired by frost and water stresses near the ground. Also, the allelochemical properties of shrubs had negative effects on seed germination. For the seedling stage, large temperature amplitudes and freezing events during the growing season, as well as the extremely low temperature during winter, were important factors affect seedling mortality. Also the low-temperature photoinhibition resulted from the combination of low temperature and high sunlight significantly decreased seedling photosynthesis during the growing season. Besides, frost-heave activity induced by large soil temperature amplitude and soil water deficits during summer impeded seedling establishment at and above the treeline. Snowpack could keep the seedlings away from the extremely low air temperature during the winter and supply snowmelt water in the early growing season. However, too long duration of the snowpack might increase the possibility of fungal infection that promote seedling mortality. Dense shrub and grass cover above the treeline and the presence of herbivores might decrease seedling survival. In all, the influence of climate warming on seedling establishment across the timberline ecotone is complex and uncertain. Further research is needed to explore the exact effects of warmth-induced environmental changes to seedling recruitment at the alpine treeline. Since the beginning of the growing season might advance under scenarios of climate warming, which in turn led to more early-season freezing events at and above the treeline, it is important to define the temperature threshold of freezing events to analyze the relationship between growing-season freezing events and increasing temperature in the future. Based on this threshold, we can further disclose the effects of growing-season freezing events on seedling establishment at alpine treeline, which will be helpful to elucidate treeline formation and predict treeline dynamics under future climate change.