The rapid increase in plastic production has led to significant environmental challenges due to the accumulation of nondegradable plastic waste, underscoring the urgent need for sustainable alternatives. Nanocellulose, the most abundant renewable biopolymer on Earth, has emerged as a promising candidate for next-generation film materials. This review explores the potential of nanocellulose films as a sustainable replacement for conventional oil-derived plastic films, focusing on its hierarchical structure, tunable properties, and diverse functionalities. The design and assembly principles of hierarchical architectures, such as aligned, cholesteric, and random structures, are discussed as key strategies for optimizing performance. By understanding the structure-property relationships, we examine how nanocellulose-based films can be tailored for applications in electronics, optics, environment, and packaging. This review not only provides insights into advanced design and assembly principles for sustainable materials but also paves the way for innovative applications, offering a pathway to reduce the carbon footprint and environmental impact of traditional plastics.