Transactions listed are from October 1 of previous year to April 1 of the following year.
- January 22, 1918
- March 8, 1918
- March 18, 1918
As part of a 3-team trade, traded Tim Hendryx to the St. Louis Browns. Received a player to be named later from the Cincinnati Reds. In addition, the St. Louis Browns sent Lee Magee to the Cincinnati Reds. The Cincinnati Reds sent Tommy Clarke (April 25, 1918) to the New York Yankees to complete the trade.
- May 24, 1918
Purchased Happy Finneran from St Paul (American Association).
- June 19, 1918
- June 20, 1918
Purchased Hank Robinson from Little Rock (Southern Association).
- July 19, 1918
- September 21, 1918
Drafted Lefty O'Doul from Salt Lake City (PCL) in the 1918 rule 5 draft.
- December 9, 1918
- December 15, 1918
Signed Jack Quinn as a free agent. (League ruled player was New York Yankees property following procedural claim by club). (Date given is approximate. Exact date is uncertain.)
- December 18, 1918
- March 6, 1919
- March 15, 1919
- March 21, 1919
Sold Cliff Markle to Salt Lake City (PCL).