| | | | | | | | | | |  | Major Transactions |
| | | | Tuesday, September 6th, 1966 | | Signed SP B. Veale to a 3-year contract extension worth a total of $570,000. |
| Saturday, July 2nd, 1966 | | Signed CL T. Butters to a 3-year contract extension worth a total of $900,000. |
| Wednesday, June 1st, 1966 | | MR B. Tiefenauer was designated for assignment and placed on waivers. | | Purchased the contract of MR J. Wyatt from Triple A Columbus. |
| Tuesday, May 17th, 1966 | | Signed 2B B. Mazeroski to a 2-year contract extension worth a total of $380,000. |
| Wednesday, April 20th, 1966 | | Demoted CF V. Davalillo to Triple A Columbus. | | Purchased the contract of CF B. Tolan from Triple A Columbus. | | LF A. Johnson was designated for assignment and placed on waivers. | | LF H. Goss was designated for assignment and placed on waivers. | | CF L. Elliot was designated for assignment and placed on waivers. | | CF M. Stanley was designated for assignment and placed on waivers. |
| Wednesday, February 16th, 1966 | | Signed free agent SS J. Pagan to a 1-year contract worth a total of $30,000. |
| Wednesday, December 29th, 1965 | | Signed free agent MR J. Wyatt to a 2-year contract worth a total of $60,000. |
| Monday, December 27th, 1965 | | Signed free agent MR B. Tiefenauer to a 1-year contract worth a total of $40,000. |
| Monday, December 20th, 1965 | | Signed LF T. Davis to a 3-year contract extension worth a total of $4,400,000. |
| Wednesday, December 15th, 1965 | | Placed SP M. Koyama on the active roster. | | Placed MR L. Sherry on the active roster. |
| Tuesday, December 14th, 1965 | | Signed free agent MR L. Sherry to a 1-year contract worth a total of $102,999. |
| Saturday, December 11th, 1965 | | Signed free agent SP M. Koyama to a 3-year contract worth a total of $1,865,998. |
| Tuesday, November 16th, 1965 | | MR B. Fischer becomes a free-agent. | | C R. Hundley received a 1-year contract through automatic renewal worth a total of $24,774. | | SP T. John received a 1-year contract through automatic renewal worth a total of $24,774. | | SS G. Alley received a 1-year contract through automatic renewal worth a total of $24,774. | | MR T. Sisk received a 1-year contract through automatic renewal worth a total of $24,774. | | MR T. Davidson received a 1-year contract through automatic renewal worth a total of $24,774. | | Placed RF R. Clemente on the active roster. |
| Saturday, November 13th, 1965 | | 3B B. Bailey received a 1-year contract through arbitration worth a total of $56,194. | | SP B. Veale received a 1-year contract through arbitration worth a total of $127,926. | | CF V. Davalillo received a 1-year contract through arbitration worth a total of $24,774. | | 1B D. Clendenon received a 1-year contract through arbitration worth a total of $107,088. | | SP J. Lamabe received a 1-year contract through arbitration worth a total of $174,694. | | CL T. Butters received a 1-year contract through arbitration worth a total of $227,968. | | SP A. McBean received a 1-year contract through arbitration worth a total of $61,912. | | 1B W. Smith received a 1-year contract through arbitration worth a total of $227,456. | | C B. Freehan received a 1-year contract through arbitration worth a total of $568,832. | | RF W. Stargell received a 1-year contract through arbitration worth a total of $266,392. |
| Monday, November 8th, 1965 | | Signed free agent RF R. Clemente to a 2-year contract worth a total of $98,000. |
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