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
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

T. Rowe Price Investment Management
T. Rowe Price Investment Management Baltimore, Maryland $145B AUM 22.78% 1-Year Est. Return
HKAM
Horizon Kinetics Asset Management New York $9.23B AUM 27.52% 1-Year Est. Return
Susquehanna International Group
Susquehanna International Group Bala Cynwyd, Pennsylvania $893B AUM 36.07% 1-Year Est. Return
BlackRock
BlackRock New York $5.72T AUM 30.48% 1-Year Est. Return
Citadel Advisors
Citadel Advisors Miami, Florida $618B AUM 30.34% 1-Year Est. Return
Invesco
Invesco Atlanta, Georgia $1.02T AUM 30.18% 1-Year Est. Return
Alyeska Investment Group
Alyeska Investment Group Chicago, Illinois $35.4B AUM 33.54% 1-Year Est. Return
VCM
Vanguard Capital Management Malvern, Pennsylvania $4.04T AUM
VPM
Vanguard Portfolio Management Malvern, Pennsylvania $1.91T AUM
Adage Capital Partners
Adage Capital Partners Boston, Massachusetts $64.8B AUM 42.7% 1-Year Est. Return

William Blair & Company's MIAX Position: Q1 2026 in Review

William Blair & Company increased its Miami International Holdings (MIAX) stake by 1.7% in Q1 2026, buying an estimated $451K and bringing the position to 665,781 shares worth $25.9M. The position accounts for 0.07% of the portfolio, ranked #215.

William Blair & Company first reported a position in MIAX in Q3 2025 and has held it in 3 quarters since. The position peaked at $29.1M in Q4 2025. 201 funds tracked by Wall St. Rank hold MIAX as of Q1 2026.

  • William Blair & Company held 665,781 shares of Miami International Holdings worth $25.9M as of Q1 2026.
  • William Blair & Company bought 10,936 Miami International Holdings shares in Q1 2026, an estimated $451K.
  • Miami International Holdings made up 0.07% of William Blair & Company's portfolio in Q1 2026, its #215 holding.
  • William Blair & Company first reported a position in Miami International Holdings in Q3 2025 and has held it in 3 quarters since.
  • William Blair & Company's Miami International Holdings position peaked at $29.1M in Q4 2025.
  • 201 funds tracked by Wall St. Rank held Miami International Holdings as of Q1 2026.

Based on William Blair & Company's 13F filing for Q1 2026, filed 8 May 2026.