About
Justin So holds a Master's degree in Computer Science from the University of Pennsylvania and previously worked in a finance role at Arm. He is co-founder and CEO of Sidekick.
Founder at SidekickYC S26
Intro paths
YC
Justin went through Y Combinator (Summer 2026) — any YC alum in your network can reach them through the YC community.
GP
Their group partner at YC was Aaron Epstein, General Partner at Y Combinator — the partner who ran Sidekick's batch and knows the company first-hand. YC profile ↗
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In turn, Justin can intro founders to Sidekick's investors below.
Sidekick's investors · 1
Experience
- Sidekick (YC S26)Founder and CEOcurrent2025 — presentSan Francisco, CA
- ArmFinance Analyst2025 — 2026San Jose, CA
Skills & more
Python (Programming Language)2Microsoft PowerPointMicrosoft ExcelMicrosoft OutlookFinancial Analysis1InvestmentsFinancial ModelingEconomicsDue Diligence1Business AnalysisAccountingLeadership4
+4 more
TeamworkProblem SolvingPersistenceAnalytical SkillsLanguages English · Korean · Spanish
From Justin's professional profile.
Frequently asked questions
- Who is Justin So?
- Justin So holds a Master's degree in Computer Science from the University of Pennsylvania and previously worked in a finance role at Arm. He is co-founder and CEO of Sidekick.
- Where does Justin So work?
- Justin So is Founder of Sidekick.
- What companies did Justin So found?
- Justin So founded Sidekick.
- Where did Justin So go to school?
- Justin So studied at Y Combinator; University of Pennsylvania (Master's degree, Computer Science); UC Santa Barbara (Bachelor's degree, Economics).
Founder mafias
Y Combinator mafia8,773
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Sam AltmanPresidentFounded Tools for Humanity +3Jessica LivingstonCo-founderFounded Y CombinatorAlexis OhanianYC Summer 2005Founded RedditFred EhrsamYC Summer 2012Founded Nudge +1Matt HuangYC Winter 2011Founded HotspotsTrae StephensYC Winter 2022Founded Pursuit +1
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University of Pennsylvania mafia201
Also came through, then founded or led a company.
Kunal BahlSystems EngineeringFounded SnapdealScott Wolf, MDBAFounded Cardiac Dimensions +3Ben LererBSFounded Thrillist +1Eric HeilBSEFounded Ladderbio +1Trevor PriceB.A.Founded Quilted Health +1Lyle BerkowitzBSEFounded Apollo Health +1
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UC Santa Barbara mafia61
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Logan GreenBAFounded Lyft +1Nils ReggeBAFounded Developx +2Michael WitzbaFounded Mob Science +2Brett GibsonBAFounded Slinkset +1Ivan BercovichPhDFounded Unwrap +1Zheng XuPh.D.Founded SolarCity +1
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Lynbrook High School mafia16
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Same school
Also attended Y Combinator2,000
Tarek MansourCo-founder & CEO of KalshiSuhail DoshiFounder of Mixpanel; founder of ParticleSubomi OluwalanaCo-founder & CEO of ConvoyMaroof AhmedFounder at Octopus VenturesJustin SwartPartner at Bitkraft Esports VenturesCollin WallaceGeneral Partner at Lobby Capital
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Also attended University of Pennsylvania824
Brian ActonCo-founder of WhatsApp; co-founder of Signal FoundationKunal BahlCo-founder of Snapdeal; co-founder of Titan CapitalDasha MaggioPartner at Felicis Ventures, writer on venture capital and founder psychologyNancy WangInvestor at Felicis VenturesLeah von SiemensPartner at Manta Ray VenturesEghosa OmoiguiFounder and Managing General Partner at EchoVC Partners
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Also attended UC Santa Barbara235
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Also attended Lynbrook High School23
Damir BecirovicInvestor at Index VenturesHariFellow at Clear VenturesAkshay NathanEngineering Manager at Asymmetric Capital PartnersLynn Stepovich CarterOperating Partner, Talent & Growth at Operator CollectiveKevin TuPartner at DFJYoni ZemlyakInvestor at Light Street Capital
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Shared employers
Also worked at Arm31
Simon SegarsExecutive Advisor at Black Opal VenturesBruce BeckloffCo Founder & CEO at Bloc VenturesMichael DimelowCCO at Bloc VenturesAndy GreenNon Executive Director at Bloc VenturesBianca FurtunaHead of Data Science at Founders FactoryNathan YadlinGeneral Partner at Palsar Ventures
+ 25 more