Kansas City Royals vs Seattle Mariners All-Time Record

American League
Kansas City Royals
Seattle Mariners
Royals lead Mariners250to242since 1977

Retrosheet history through 2025, plus 6 final games from the current feed.

2026 season series: Royals lead 5-1

By

Data updated 6 min read

At a glance

All-time since 1977 · current-feed analysis, 2002 to 2026

Kansas City Royals vs Seattle Mariners insights

Current-feed record
+22wins for Mariners
56% Mariners · 44% Royals

The split has held steady across the schedule change: 14-12 since 2023.

Recent form
11-9last 20
Royals on a 2-game streak

Royals won 8-6 on May 24, 2026

Where it matters
0Postseason games

No postseason meetings since 2002.

Schedule context
  • Mariners built the series lead before the 2023 schedule change, taking 87 of 154 decided meetings (56%).
  • Since the schedule balanced out they are 14-12, or 54% to Mariners.

Royals vs Mariners complete all-time series record

Kansas City Royals and Seattle Mariners have met 492 times since 1977, never in the postseason. 312 meetings predate the current feed, which adds game-level detail from 2002.

History span
1977 to 2026
First and latest meeting
Before 2002
312
Meetings from the Retrosheet game logs
Since 2002
180
Meetings with game-level detail below
Win Percentage
79W
101W
KC
SEA
44%56%
Kansas City RoyalsSeattle Mariners

Recent Games

Last 10 Games
May 24
KC 8-6 SEA
KC
May 23
KC 5-0 SEA
KC
May 22
KC 0-2 SEA
SEA
May 3
SEA 1-4 KC
KC
May 2
SEA 2-3 KC
KC
May 1
SEA 6-7 KC
KC
Sep 18
KC 0-2 SEA
SEA
Sep 17
KC 7-5 SEA
KC
Sep 16
KC 5-12 SEA
SEA
Jul 3
SEA 2-3 KC
KC
Last Meeting
May 24, 2026Final
KC
8
HOME
SEA
6
AWAY
Royalswon by2runs
Royals' 2nd straight in this series·Game 180 since 2002
Streaks & Momentum
Current Streak
Kansas City Royals: 2 consecutive wins
2
Avg. Margin of Victory
Games decided by 3.6 runs on average
3.6runs
Momentum (Last 10 vs Archive since 2002)
KC↑Trending Up
Last 1070%
Archive since 200243.9%
SEA↓Trending Down
Last 1030%
Archive since 200256.1%
Last 10 Results
KC / SEA

Record since 2002

Season Split & Biggest Wins
Regular season vs Postseason record, plus each team's largest margin of victory
Regular Season180 games
79
101
No postseason meetings appear since 2002.
Kansas City Royals Biggest Win
17–3+14 runs
Jul 3, 2007
Seattle Mariners Biggest Win
16–3+13 runs
Aug 17, 2004
Decade Breakdown
Choose a decade to scope the current-feed page
Season by Season
Season ↓KC ↕SEA ↕Games ↕
2026516
2025347
2024336
2023167
2022246
2021437
2019257
2018156
2017527
2016347
2015426
2014257
2013437
2012178
2011538
2010549
2009549
2008729
2007369
2006358
2005279
2004257
2003459
2002369

All 24 seasons are shown in the table above.

Home / Away Split
43-51KC HOME50-36SEA HOME
AWAY
36-50
KC
AWAY
51-43
SEA
Retrosheet archiveComplete through 2025

Kansas City Royals vs Seattle Mariners all-time record, 1977 to 2025

Explore how this matchup changed by decade, where each lineup produced its runs, and the games that pushed the rivalry record book. This archive is a separate source window from the current-feed sections above, which start in 2002.

Games
486
Peak inning
1
Record game
25 runs
Two source windows. Current-feed sections: 180 games from 2002 to 2026. History Lab: 486 Retrosheet games from 1977 to 2025. The first refreshes with current finals; Retrosheet's published archive currently ends in 2025.

Decade balance

Select an era to inspect pace, scoring and attendance.

The information used here was obtained free of charge from and is copyrighted by Retrosheet. Interested parties may contact Retrosheet at www.retrosheet.org.

Open source archive

Betting Context

Betting context since 2002

How this pairing has settled: run margins, totals and break-even prices derived from its historical record. These are final-score frequencies, not results against a closing line. We do not hold historical sportsbook prices for these games.

One-run games
26.1%

Share of the 180 decided meetings settled by exactly one run.

Won by 2 or more
73.9%

A 2+ run margin crosses 1.5, but this is not a historical line result. Average gap: 3.6.

Average total
9.5runs

Final-score average without accounting for park, bullpen or weather.

Home side wins
51.7%

Share of decided meetings won by the listed home team.

Totals ladder

Where the combined score landed against the half-run lines a book normally posts. Half runs cannot push, so every meeting falls on one side.

LineOverUnderOver rate
7.510575
58.3%
8.59783
53.9%
9.5Closest to even8793
48.3%

Fair price from the base rate

The decimal price that corresponds exactly to each club's win share in this archive. It describes the record and does not estimate the next game.

Seattle Mariners
101 W · 56.1%1.78
Kansas City Royals
79 W · 43.9%2.28

A base rate is not a forecast. Starting pitchers, lineups, injuries and venue all matter more to a single game than a multi-season head-to-head record.

Last 20 meetings vs full history

One-run games
35%vs 26.1% full archive
+8.9% in the last 20
Won by 2 or more
65%vs 73.9% full archive
-8.9% in the last 20
Average total
8.5 runsvs 9.5 runs full archive
-1 runs in the last 20

Seasons 2023 to 2026. The comparison shows whether the last 20 final scores differ from the longer archive, without assigning a cause or predicting what comes next.

View the break-even percentages in another odds format with the odds converter, or compare current prices for Mariners and Royals in the oddsmatcher.

Questions about this record: Kansas City Royals vs Seattle Mariners

How do recent Kansas City Royals vs Seattle Mariners results compare with the complete record?

Kansas City Royals have won 7 of the latest 10 decided meetings. Kansas City Royals lead the decided record 250-242. The recent window is a subset of the complete series from 1977 through 2026, so the page reports the two separately.

When did the Kansas City Royals and Seattle Mariners first play each other?

The Retrosheet archive's first recorded meeting for this pairing is Apr 22, 1977, when Kansas City Royals won 6-5 away to Seattle Mariners. The archive covers 486 meetings from 1977 through 2025. The current feed starts in 2002 and is reported separately.

About Erik Andersson

Erik Andersson is SharkBetting's Content & Marketing Specialist. His published work focuses on betting methodology, market analysis, regulation and consumer education.

The source windows, derivations and update process for this data page are documented in the methodology above.

View full profile →

Methodology & Data Sources

Current MLB game logs come from the balldontlie API and cover the 2002 season onward. Scores and schedule anomalies are checked against the official MLB Stats API. Spring training is excluded, while results from earlier franchise identities are merged into the current club.

The all-time record and the History Lab use Retrosheet game logs through 2025, with inning lines, team totals, attendance, duration and ballpark fields when available. Final games after 2025 come from the current feed, and every section built on that feed alone is labeled as starting in 2002.

The betting context summarizes completed final scores only. It contains no sportsbook closing lines and summarizes only completed games. Report a possible error through our contact page with the matchup and game date.

Read the full H2H data methodology →

Last updated Sources: balldontlie, MLB Stats API, Retrosheet

Kansas City Royals and Seattle Mariners have met 180 times in this archive, which covers the 2002 season onward.