<p>This study examines the asymmetric volatility spillovers and interconnectedness among 15 major cryptocurrencies using high-frequency data at 5-min intervals. We adopt a comprehensive methodology to analyze both symmetric and asymmetric volatility, using realized volatility and semi-variances to capture positive and negative spillovers. We decompose volatility spillovers into short- and long-term frequency bands to provide insights into the directional and temporal aspects of volatility dynamics. Our findings reveal significant asymmetric spillovers, with negative volatility spillovers persistently dominating positive ones across total, short-term, and long-term horizons, particularly during turbulent periods such as the COVID-19 pandemic and the Russia–Ukraine War. Short-term spillovers are the most pronounced, reflecting rapid contagion driven by downside risk and investor sentiment, while long-term dynamics exhibit alternating phases shaped by macroeconomic, political, and regulatory conditions, with negative volatility remaining the primary driver during stress episodes. Additionally, exogenous factors such as environmental attention (ICEA), cryptocurrency policy uncertainty (UCRY), CBDC-related uncertainty, US economic policy uncertainty (USEPU), and global risk and sentiment indicators significantly affect cryptocurrency connectivity in a heterogeneous and horizon-dependent manner. This study offers valuable insights into diversification strategies for cryptocurrency portfolios and informs regulatory bodies on market stability and risk management, particularly during turbulent periods.</p>