u/drkspace2

The Braves have now gone 11 straight series to start the season without losing. It's always a question in the post game threads/generally "What's the longest streak to start the season? How close are these Braves to the record?"

tl;dr Not close. The 1970 Reds were insane to start the season and went 32 (or 31 depending on how you count series) series in a row without losing. This is the also the record for any time in a season.

Note: These numbers are counting single game series as full series. Some of the older teams will have a series or two less if you do not want to count those.

Longest streaks ever:

Length	Team Abbrev	Start Date	Last Date
32	Cincinnati Reds	1970-04-06	1970-07-20
26	Detroit Tigers	1934-07-02	1934-09-29
22	Los Angeles Dodgers	2017-06-09	2017-08-21
22	Atlanta Braves	2002-05-10	2002-07-22
21	St. Louis Cardinals	1942-07-31	1942-09-26
21	New York Yankees	1941-06-20	1941-08-15
21	New York Giants	1927-07-24	1927-10-02
21	Chicago Cubs	1918-04-24	1918-07-14
21	Brooklyn Dodgers	1916-05-13	1916-08-08
20	New York Yankees	1998-04-17	1998-06-12
20	Detroit Tigers	1935-06-22	1935-09-02
19	Oakland Athletics	1971-04-09	1971-06-08
19	New York Yankees	1928-04-29	1928-07-06
18	St. Louis Cardinals	1943-05-07	1943-07-08
18	New York Yankees	1954-05-28	1954-07-20
18	Minnesota Twins	1965-04-12	1965-06-04
18	Los Angeles Dodgers	2013-06-18	2013-08-19
18	Brooklyn Dodgers	1920-08-09	1920-10-03
18	Boston Red Sox	1912-06-05	1912-08-21
17	New York Yankees	1932-05-06	1932-06-30
17	New York Giants	1954-05-31	1954-07-21
17	Kansas City Royals	1980-07-03	1980-08-28
17	Cleveland Guardians	2017-08-03	2017-09-29
17	Chicago Cubs	1929-06-27	1929-08-26
17	Atlanta Braves	1996-04-11	1996-06-03

Longest streaks to start a season:

Length	Team Abbrev	Start Date	Last Series Date
32	Cincinnati Reds	1970-04-06	1970-07-20
18	Minnesota Twins	1965-04-12	1965-06-04
15	Philadelphia Phillies	1950-04-18	1950-05-26
15	Philadelphia Athletics	1914-04-14	1914-06-14
15	Detroit Tigers	1911-04-12	1911-06-01
14	Minnesota Twins	1970-04-07	1970-05-18
14	Los Angeles Dodgers	1977-04-07	1977-05-24
14	Cincinnati Reds	1944-04-18	1944-06-02
14	Baltimore Orioles	1997-04-01	1997-05-12
13	San Francisco Giants	1962-04-10	1962-05-18
13	Los Angeles Dodgers	2020-07-23	2020-09-01
13	Detroit Tigers	1947-04-15	1947-05-18
12	Pittsburgh Pirates	1937-04-20	1937-05-21
12	Philadelphia Phillies	1995-04-26	1995-06-01
12	New York Giants	1917-04-11	1917-06-01
12	Los Angeles Dodgers	1965-04-12	1965-05-17
12	Los Angeles Dodgers	1962-04-10	1962-05-15
12	Cleveland Guardians	1920-04-14	1920-05-31
12	Boston Red Sox	1939-04-18	1939-05-19
12	Arizona Diamondbacks	2018-03-29	2018-05-08
11	New York Yankees	1955-04-12	1955-05-06
11	Detroit Tigers	1945-04-17	1945-05-23
11	Boston Red Sox	1946-04-16	1946-05-14
11	Atlanta Braves	2026-03-27	---

Tools used: boxball with retrosheets. Here is the link to the code

Edit: The 1970 reds did tie their 8th series with the Cardinals. The first game of the series was postponed and they won the makeup https://www.baseball-reference.com/boxes/SLN/SLN197007201.shtml.

Edit 2: Fixed formatting