William Blair & Company
MIAX

William Blair & Company’s Miami International Holdings MIAX Stock Holding History

William Blair & Company’s Portfolio MIAX Stock Details MIAX Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q2 		$65.8M Buy
1,769,432
+1,103,651
+166% +$49.4M 0.17% 122
2026
Q1 		$25.9M Buy
665,781
+10,936
+2% +$451K 0.07% 215
2025
Q4 		$29.1M Buy
654,845
+291,080
+80% +$13M 0.08% 187
2025
Q3 		$14.6M Buy
+363,765
New +$13.3M 0.04% 281

Other funds holding MIAX

HKAM
Horizon Kinetics Asset Management New York $8.82B AUM 23.05% 1-Year Est. Return
BlackRock
BlackRock New York $6.73T AUM 46.02% 1-Year Est. Return
T. Rowe Price Investment Management
T. Rowe Price Investment Management Baltimore, Maryland $153B AUM 38.14% 1-Year Est. Return
Vanguard Portfolio Management
Vanguard Portfolio Management Malvern, Pennsylvania $2.22T AUM
Susquehanna International Group
Susquehanna International Group Bala Cynwyd, Pennsylvania $1.28T AUM 58.89% 1-Year Est. Return
Vanguard Capital Management
Vanguard Capital Management Malvern, Pennsylvania $4.68T AUM
Invesco
Invesco Atlanta, Georgia $1.26T AUM 61.52% 1-Year Est. Return
JD6
J Digital 6 Chicago, Illinois $169M AUM 111.5% 1-Year Est. Return
Balyasny Asset Management
Balyasny Asset Management Chicago, Illinois $80.2B AUM 51.53% 1-Year Est. Return
American Century Companies
American Century Companies Kansas City, Missouri $226B AUM 44.75% 1-Year Est. Return

William Blair & Company's MIAX Position: Q2 2026 in Review

William Blair & Company increased its Miami International Holdings (MIAX) stake by 166% in Q2 2026, buying an estimated $49.4M and bringing the position to 1,769,432 shares worth $65.8M. The position accounts for 0.17% of the portfolio, ranked #122.

William Blair & Company first reported a position in MIAX in Q3 2025 and has held it in 4 quarters since. 206 funds tracked by Wall St. Rank hold MIAX as of Q2 2026.

  • William Blair & Company held 1,769,432 shares of Miami International Holdings worth $65.8M as of Q2 2026.
  • William Blair & Company bought 1,103,651 Miami International Holdings shares in Q2 2026, an estimated $49.4M.
  • Miami International Holdings made up 0.17% of William Blair & Company's portfolio in Q2 2026, its #122 holding.
  • William Blair & Company first reported a position in Miami International Holdings in Q3 2025 and has held it in 4 quarters since.
  • 206 funds tracked by Wall St. Rank held Miami International Holdings as of Q2 2026.

Based on William Blair & Company's 13F filing for Q2 2026, filed 11 Aug 2026.