William Blair & Company
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William Blair & Company’s Monolithic Power Systems MPWR Stock Holding History

William Blair & Company’s Portfolio MPWR Stock Details MPWR Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q1 		$33.4M Buy
30,557
+16,910
+124% +$18.5M 0.1% 181
2025
Q4 		$12.4M Buy
13,647
+3,465
+34% +$3.33M 0.03% 319
2025
Q3 		$9.37M Buy
10,182
+1,195
+13% +$969K 0.03% 376
2025
Q2 		$6.57M Sell
8,987
-521
-5% -$332K 0.02% 436
2025
Q1 		$5.51M Sell
9,508
-1,850
-16% -$1.17M 0.02% 459
2024
Q4 		$6.72M Buy
11,358
+1,759
+18% +$1.27M 0.02% 419
2024
Q3 		$8.87M Buy
9,599
+1
+0% +$863 0.03% 364
2024
Q2 		$7.89M Buy
9,598
+113
+1% +$81.5K 0.02% 376
2024
Q1 		$6.43M Sell
9,485
-1,990
-17% -$1.33M 0.02% 419
2023
Q4 		$7.24M Sell
11,475
-33
-0.3% -$17.2K 0.02% 379
2023
Q3 		$5.32M Sell
11,508
-10,369
-47% -$5.3M 0.02% 423
2023
Q2 		$11.8M Sell
21,877
-1,485
-6% -$705K 0.04% 288
2023
Q1 		$11.7M Buy
23,362
+67
+0.3% +$30.8K 0.05% 279
2022
Q4 		$8.24M Buy
23,295
+3,396
+17% +$1.22M 0.04% 326
2022
Q3 		$7.23M Buy
19,899
+6,616
+50% +$2.94M 0.03% 340
2022
Q2 		$5.1M Buy
13,283
+2,948
+29% +$1.25M 0.02% 414
2022
Q1 		$5.02M Buy
10,335
+883
+9% +$385K 0.02% 465
2021
Q4 		$4.66M Buy
9,452
+2,469
+35% +$1.27M 0.01% 492
2021
Q3 		$3.38M Sell
6,983
-3,273
-32% -$1.49M 0.01% 555
2021
Q2 		$3.83M Sell
10,256
-316
-3% -$111K 0.01% 526
2021
Q1 		$3.73M Buy
10,572
+97
+0.9% +$35.3K 0.01% 524
2020
Q4 		$3.84M Buy
10,475
+237
+2% +$76K 0.01% 492
2020
Q3 		$2.86M Buy
10,238
+70
+0.7% +$18.2K 0.01% 509
2020
Q2 		$2.41M Sell
10,168
-204
-2% -$41.3K 0.01% 516
2020
Q1 		$1.74M Buy
10,372
+1,807
+21% +$310K 0.01% 543
2019
Q4 		$1.52M Buy
8,565
+151
+2% +$24.1K 0.01% 670
2019
Q3 		$1.31M Buy
8,414
+5,901
+235% +$882K 0.01% 677
2019
Q2 		$341K Sell
2,513
-1,329
-35% -$181K ﹤0.01% 1109
2019
Q1 		$521K Buy
3,842
+962
+33% +$126K ﹤0.01% 953
2018
Q4 		$335K Sell
2,880
-558
-16% -$66.8K ﹤0.01% 1049
2018
Q3 		$432K Sell
3,438
-1,846
-35% -$257K ﹤0.01% 1004
2018
Q2 		$706K Sell
5,284
-1,350
-20% -$172K ﹤0.01% 833
2018
Q1 		$768K Sell
6,634
-100
-1% -$11.9K 0.01% 781
2017
Q4 		$757K Sell
6,734
-50
-0.7% -$5.8K 0.01% 822
2017
Q3 		$723K Hold
6,784
– – 0.01% 811
2017
Q2 		$654K Buy
6,784
+166
+3% +$15.8K ﹤0.01% 886
2017
Q1 		$586K Sell
6,618
-2,384
-26% -$211K ﹤0.01% 860
2016
Q4 		$738K Sell
9,002
-2,213
-20% -$178K 0.01% 713
2016
Q3 		$903K Buy
11,215
+1,434
+15% +$106K 0.01% 671
2016
Q2 		$668K Hold
9,781
– – 0.01% 721
2016
Q1 		$622K Sell
9,781
-10,665
-52% -$636K 0.01% 726
2015
Q4 		$1.3M Sell
20,446
-6,650
-25% -$413K 0.01% 565
2015
Q3 		$1.39M Buy
+27,096
New +$1.34M 0.01% 644
2014
Q4 		– Sell
-18,796
Closed -$827K – 2130
2014
Q3 		$827K Sell
18,796
-25,114
-57% -$1.1M ﹤0.01% 1537
2014
Q2 		$1.86M Sell
43,910
-344,540
-89% -$13.4M ﹤0.01% 1264
2014
Q1 		$15.1M Buy
+388,450
New +$13.7M 0.02% 678
2013
Q4 		– Sell
-333,893
Closed -$10.1M – 2021
2013
Q3 		$10.1M Sell
333,893
-401,475
-55% -$11.3M 0.02% 736
2013
Q2 		$17.7M Buy
+735,368
New +$17.5M 0.04% 513

Other funds holding MPWR

BlackRock
BlackRock New York $5.72T AUM 30.48% 1-Year Est. Return
Fidelity Investments
Fidelity Investments Boston, Massachusetts $1.9T AUM 41.92% 1-Year Est. Return
VCM
Vanguard Capital Management Malvern, Pennsylvania $4.04T AUM
VPM
Vanguard Portfolio Management Malvern, Pennsylvania $1.91T AUM
Invesco
Invesco Atlanta, Georgia $1.02T AUM 30.18% 1-Year Est. Return
State Street
State Street Boston, Massachusetts $2.9T AUM 29.55% 1-Year Est. Return
Geode Capital Management
Geode Capital Management Boston, Massachusetts $1.61T AUM 30.72% 1-Year Est. Return
T. Rowe Price Associates
T. Rowe Price Associates Baltimore, Maryland $865B AUM 30.76% 1-Year Est. Return
Franklin Resources
Franklin Resources San Mateo, California $408B AUM 30.18% 1-Year Est. Return
T. Rowe Price Investment Management
T. Rowe Price Investment Management Baltimore, Maryland $145B AUM 22.78% 1-Year Est. Return

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

William Blair & Company increased its Monolithic Power Systems (MPWR) stake by 124% in Q1 2026, buying an estimated $18.5M and bringing the position to 30,557 shares worth $33.4M. The position accounts for 0.1% of the portfolio, ranked #181.

William Blair & Company first reported a position in MPWR in Q2 2013 and has held it in 48 quarters since. 1,114 funds tracked by Wall St. Rank hold MPWR as of Q1 2026.

  • William Blair & Company held 30,557 shares of Monolithic Power Systems worth $33.4M as of Q1 2026.
  • William Blair & Company bought 16,910 Monolithic Power Systems shares in Q1 2026, an estimated $18.5M.
  • Monolithic Power Systems made up 0.1% of William Blair & Company's portfolio in Q1 2026, its #181 holding.
  • William Blair & Company first reported a position in Monolithic Power Systems in Q2 2013 and has held it in 48 quarters since.
  • 1,114 funds tracked by Wall St. Rank held Monolithic Power Systems as of Q1 2026.

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