Maize is an important staple crop for smallholder farmers across sub-Saharan Africa. Yet gender-based opportunities, constraints, and dynamics in maize value chains are under-researched. A better understanding is necessary for gender-sensitive policy and development interventions. This study thus examines gender relations across the maize value chain in Tanzania, looking at gendered participation, decision-making patterns, and resources in maize/seed production, marketing, and sales. Data were collected using mixed methods: a survey of 551 households, key informant interviews, and focus group discussions. Our findings show that the higher nodes of the maize value chain are dominated by men. Women's participation is generally limited to maize production, and women face barriers to entry into higher nodes. Where they do participate in buying, trading, or retail, they face barriers to expansion of their business. Gendered decision-making patterns with regards to maize sales show regional variation, but overall men are primary decision-makers. Gender mainstreaming and gender transformative interventions targeted at higher nodes in the maize value chain are needed.