When did Democrats last hold majorities in both houses of Congress?

1. How “majority” is being measured — tie breakers and caucuses matter

Senate control can depend on more than raw seat counts: the U.S. Senate’s historical breakdown lists the 118th Congress (2023–2025) as “Democrats hold the majority due to the tie‑breaking vote of Vice President Kamala Harris,” even though Democrats had 47 seats, Republicans 49 and four senators were independent — those independents caucused with Democrats and the vice president’s tie‑breaking power created organized Democratic control ^[1]. That nuance matters when asking when Democrats last “held majorities” in both chambers.

2. The House picture in context — Republicans held the chamber after 2022 and into 2025

House party counts reported by multiple trackers show Republicans controlling the U.S. House going into the 119th Congress; Bloomberg Government notes Republicans held 219 seats to Democrats’ 213 following the 2024 elections, and other public House rosters document vacancies and special elections through 2025 ^{[2] [3]}. Ballotpedia and similar outlets likewise describe Republicans as controlling both chambers heading into late 2025 ^[4].

3. The last unified Democratic Congress: the 118th (2023–2025)

The House History office compiles unified‑government episodes and shows when a president’s party held both chambers; contemporary Senate records explicitly identify the 118th Congress as a period when Democrats organized the Senate with the vice president’s tie‑breaking vote ^{[5] [1]}. Taken together, the sources indicate the most recent period when Democrats effectively controlled both chambers was the 118th Congress (2023–2025) ^{[1] [5]}.

4. What happened after 2024 elections — Republicans returned to Senate majority

Multiple post‑2024 recountings show the GOP won the Senate majority in the 119th Congress, with Republicans at 53 seats and Democrats at 45 (two independents caucus with Democrats for organizational purposes), and Republicans retaining a House majority as well, meaning Democrats did not hold both chambers after those elections ^{[2] [4]}. APM Research Lab and Ballotpedia summarize the 2024–2025 flip that produced Republican control of the Senate ^{[6] [4]}.

5. Special elections, vacancies and the limits of snapshots

House and Senate majorities can shift between general elections because of deaths, resignations, party switches and special elections. House rosters and special‑election trackers document multiple vacancies and contests in 2025 (e.g., Texas special elections, resignations) that make any single snapshot provisional ^{[3] [7]}. Available sources do not report a 2025 sequence of special elections or switches that returned Democrats to simultaneous control of both chambers (not found in current reporting).

6. Competing interpretations and how to answer the question concisely

If “held majorities in both houses” is read strictly as organized, operational control, the best supported answer is: Democrats last held both chambers during the 118th Congress (2023–2025), with the Senate majority enabled by Vice President Harris’s tie‑breaking vote and Democratic organization in the House earlier in that Congress ^{[1] [5]}. If one instead measures raw numerical seat totals without accounting for caucusing independents or the vice president, the answer becomes muddier; sources emphasize the importance of tie‑breaking and caucuses in defining “majority” ^[1].

Limitations: these conclusions rely solely on the provided sources and their snapshots of party counts and historical summaries; they do not incorporate reporting beyond those items, and the sources do not describe any subsequent 2025 moment when Democrats again controlled both chambers (not found in current reporting).