Mks MKSI Insider Ownership

NASDAQ MKSI

$216.10 +4.96 (+2.35%)

At close: Oct 21, 2026 · 4:00 PM EDT

Insider Holdings by Owner

13.31Mn Shares

Insider Ownership Statistics

as of 30 Sep, 2026

Insider Ownership

0.483%

▼-0.016% pp QoQ

Shares Held by Insiders

326.50K

filed for Sep 2026

▼-3.17% QoQ

Shares Outstanding

67.60Mn

67,600,000 shares

Direct Holdings

306.48K

Indirect: 20.02K

Net Shares Traded (QoQ)

-10.68K

net selling in Sep 2026

Insiders Holding Shares

with Form 4 holdings on file

Shares Owned by Insiders

Shares held % of outstanding

Latest —

Average ownership —

Peak ownership —

Shares Purchased/Sold by Insiders

Bought Sold

Latest quarter —

Net over range —

Buying quarters —

Insider Ownership Summary

Updated Oct 5, 2026

In the last 12 months, insiders at MKS made open-market sales of $43.5 million (151.75K shares) and bought no shares on the open market.

Behind MKS's open-market sales in the past 12 months were 13 insiders, and no insider bought.
John Tseng-Chung Lee (President & CEO) led open-market sales of MKS stock over the past 12 months with $13.88 million (50K shares), most recently on August 14, 2026.
MKS's latest insider trade on the open market was a sale of 300 shares for $75,288 by Elizabeth Mora (Director) on September 1, 2026.
Outside the open market, MKS insiders received 782 shares in stock awards, acquired 132.6K shares through option exercises and conversions and gave up 60.34K shares to cover taxes or exercise prices over the past 12 months.
Per Business Quant, MKSI insiders together hold 326.5K shares based on their latest Form 4 filings, or 0.48% of the 67.6Mn shares outstanding; that total is down 3.17% from 337.17K shares at the end of Q2 2026 and down 23.48% from 426.67K shares at the end of Q3 2025.
Indirect holdings, through trusts, partnerships, family members and other entities, make up 6.13% (20.02K shares) of MKS's insider total, with the other 93.87% (306.48K shares) held directly.
Per Business Quant, 15 insiders of MKSI hold shares, counting officers, directors and 10% owners who have filed a Form 4 in the past two years.
MKSI's three largest insider shareholders, per their latest Form 4 filings, are John Tseng-Chung Lee (President & CEO, 134.78K shares), Kathleen Flaherty Burke (EVP, GC & Secretary, 49.44K shares) and Gerald G. Colella (Director, 29.02K shares).
John Tseng-Chung Lee holds 41.28% of the combined insider position in MKS.
A total of 60 Form 4 filings with transactions in MKS stock were made over the past 12 months, by 16 insiders.
This summary of MKS insider activity covers Form 4 filings through September 2, 2026.

Form 4 Holdings

Insiders Holding MKSI

Insiders 21

Shares held 13.31Mn

Of outstanding 19.69%

#	Insider	Position	Direct	Indirect	Total	Share of Insiders	Last Filed
1	Group Inc. Carlyle	TenPercentOwner	0	6,482,732	6,482,732	48.7%	10 May, 2023
2	Partners Vi Cayman Holdings, L.P. Carlyle	TenPercentOwner	0	6,482,732	6,482,732	48.7%	10 May, 2023
3	John Tseng-Chung Lee	President Ceo	134,776	0	134,776	1.0%	17 Aug, 2026
4	Kathleen Flaherty Burke	Evp, Gc Secretary	49,439	0	49,439	0.4%	12 May, 2026
5	Gerald G Colella	Director	0	20,017	20,017	0.2%	28 May, 2026
6	James Alan Schreiner	Evp Coo	19,201	0	19,201	0.1%	16 Jun, 2026
7	Elizabeth Mora	Director	18,845	0	18,845	0.1%	02 Sep, 2026
8	Raj Batra	Director	16,227	0	16,227	0.1%	12 May, 2026
9	Mark Milton Gitin	Evp Gm, Psd	16,134	0	16,134	0.1%	16 Feb, 2024
10	Eric Robert Taranto	Evp Gm, Vsd	12,596	0	12,596	0.1%	12 May, 2026
11	Michelle M Warner	Director	10,852	0	10,852	0.1%	08 May, 2024
12	David Philip Henry	Evp, Global Str Mktg Gm, Msd	10,422	0	10,422	0.1%	02 Jun, 2026
13	Joseph B Donahue	Director	10,033	0	10,033	0.1%	28 May, 2026
14	Jacqueline F Moloney	Director	8,775	0	8,775	0.1%	15 May, 2026
15	Peter Iii Cannone	Director	7,794	0	7,794	0.1%	19 May, 2026
16	Wissam G Jabre	Director	5,270	0	5,270	0.0%	12 May, 2026
17	John Edward Williams	Evp Gm, Psd	4,098	0	4,098	0.0%	04 Aug, 2026
18	Geoffrey Wild	Director	1,813	0	1,813	0.0%	18 Aug, 2022
19	Michelle M Mccarthy	Svp Chief Accounting Officer	2	0	2	0.0%	08 Jun, 2026
20	Ramakumar Mayampurath	Evp Cfo	1	0	1	0.0%	26 May, 2026
21	Seth H Bagshaw	Evp, Cfo Treasurer	1	0	1	0.0%	26 Feb, 2024

Each row is that insider’s most recently reported position, from Form 4 filings over the last 60 months — which is why this total does not tie to the quarterly series above, where a quarter counts only the insiders who filed in it. Shares held through a fund or institutional portfolio are counted on the institutional ownership page instead.

Form 4 Filings

3,156 Insider Transactions

Source SEC Form 4

Latest quarter Sep 2026

Date	Insider	Position	Transaction	Shares	Price	Value	Shares Held After	Ownership
01 Sep, 2026	Elizabeth Mora	Director	Disposed S	300	$250.96	$75.29K	18,845	Direct
17 Aug, 2026	Renee Martel Donlan	Evp, Gc Cco	Acquired A	954	—	—	4,781	Direct
14 Aug, 2026	John Tseng-Chung Lee	President Ceo	Disposed S	10,000	$302.01	$3.02Mn	134,776	Direct
03 Aug, 2026	John Edward Williams	Evp Gm, Psd	Disposed S	457	$288.31	$131.76K	4,098	Direct
12 Jun, 2026	James Alan Schreiner	Evp Coo	Disposed S	2,471	$345.52	$853.79K	20,230	Direct
12 Jun, 2026	James Alan Schreiner	Evp Coo	Disposed S	812	$346.41	$281.28K	19,418	Direct
12 Jun, 2026	James Alan Schreiner	Evp Coo	Disposed S	217	$347.00	$75.30K	19,201	Direct
10 Jun, 2026	James Alan Schreiner	Evp Coo	Disposed S	781	$317.42	$247.91K	22,701	Direct
05 Jun, 2026	Michelle M Mccarthy	Svp Chief Accounting Officer	Disposed S	2,434	$315.23	$767.27K	2	Direct
01 Jun, 2026	David Philip Henry	Evp, Global Str Mktg Gm, Msd	Disposed S	6,000	$314.43	$1.89Mn	10,422	Direct
01 Jun, 2026	Elizabeth Mora	Director	Disposed S	300	$318.02	$95.41K	19,145	Direct
27 May, 2026	Gerald G Colella	Director	Disposed S	464	$330.38	$153.30K	39,553	Indirect
27 May, 2026	Joseph B Donahue	Director	Disposed S	2,100	$327.95	$688.70K	10,033	Direct
27 May, 2026	Gerald G Colella	Director	Disposed S	8,210	$331.45	$2.72Mn	31,343	Indirect
27 May, 2026	Gerald G Colella	Director	Disposed S	4,876	$332.04	$1.62Mn	26,467	Indirect
27 May, 2026	Gerald G Colella	Director	Disposed S	1,811	$335.46	$607.51K	24,656	Indirect
27 May, 2026	Gerald G Colella	Director	Disposed S	1,626	$336.54	$547.22K	23,030	Indirect
27 May, 2026	Gerald G Colella	Director	Disposed S	213	$337.05	$71.79K	22,817	Indirect
27 May, 2026	Gerald G Colella	Director	Disposed S	2,800	$338.58	$948.02K	20,017	Indirect
26 May, 2026	David Philip Henry	Evp, Global Str Mktg Gm, Msd	Disposed S	2,500	$330.50	$826.25K	16,341	Direct

Showing 1 to 20 of 3,156 transactions